I started learning to paint in 2012. I use both oil and acrylic but mostly oil. In the beginning, acrylic was easier because it dries fast but I don't enjoy it much because it is sticky and it dries fast. I vastly prefer oil, but it is a much harder medium to master. Here are some obscure technical things I have learned on the way that I wish someone had told me.
First and most important, I think, is use cheap materials! Many teachers will advise you to "buy the best you can afford", meaning artist grade paints which have the potential to cost 20 or 30 dollars a tube (or more). If you do this, you will absolutely skimp on the paint for fear of wasting the stuff and your progress will suffer. Buying the cheap stuff like Winton, 1980, Van Gogh and even Georgian is incredibly liberating. Some of these lines even offer real cads and cobalts. The important thing is to carefully compare the swatches on Blick and check the pigment numbers because these paints are not consistently good across all colors. Some colors are extremely underpigmented in some brands. But just because the paint is cheap does not mean it will not make a good painting. There are plenty of successful artists using cheap paint.
Same goes for brushes too. You don't need expensive artist brushes. Even experienced artists don't need them. There are plenty of good student brushes, Winton is one of them. Rosemary brushes are professional grade and not expensive. If you abuse a brush or forget to clean it, it's not as upsetting if it was cheap. However, some hog bristle brushes are harder to use than others. Some brands hold together at the tip and some splay. The ones that splay are hard to use for a beginner because they make an imprecise mark. Winsor & Newton ones (filberts, at least) hold together well at the tip.
My struggle is with wet in wet painting. This is my preferred method, probably because it's the hardest. It is less time consuming than layering and no worries about fat over lean.
If you paint slow, like I do, you don't want to work over the entire painting during your session. Concentrate on the area you think you can get done before it tacks up. This way, you can keep working without waiting a week for drying. If you need to work on a section that has dried, repaint some of the surrounding area so you will have wet paint to work into. It isn't always possible to do this, though, such as painting trees over a dried landscape.
Another thing I don't see mentioned that is perhaps fundamental to mastering this technique is that every stroke you make over wet paint, your brush is cutting through the paint that was already there. This is both good and bad. The good part is you can sort of erase what was already there while you lay down new paint. I guess that is why oil paint is considered "forgiving" although it feels the opposite to me. The bad part is that if this is not done with extreme skill, it usually makes mud, which brings me to my next point.
Don't assume that what you see an artist do in a video will work the same for you. For example, skillful alla prima artists can dab a brush loaded with paint over and over wet paint seemingly forever and it never makes mud. It won't work the same for you.
You can wipe or blot wet paint with a paper towel before you paint over it and it will help to keep the paint from blending so much during your stroke. And wipe your brush off before you stroke again if it picked up paint. Unless it is really oily, oil paint will naturally be resistant to gentle disturbance. If you gently blot the paint with paper towel, it won't really do anything but blur a little. In general, blotting won't ruin your work. And one of the great things about oil paint is that you can move already laid down paint around with your brush in a controlled manner. This is great for reshaping edges or correcting drawing. See my point about cutting through paint with the brush.
Here's another thing I don't find helpful: Bob Ross and other tv speed painters. Bob is why I started painting but now I wish I had not started with his technique. First, he's always talking about how easy it is--it's not. It's very prone to mud making. Second, and my biggest gripe is that his 20 minute tv programs condition you to speed through the painting. I only did a couple of paintings in his style 8 years ago, but I still have to make myself slow down because I watched his program for so many years before I ever even thought of picking up a brush. Third, it uses a TON of paint and his paints are student grade but expensive. Those big brushes waste a lot of it. And finally, his method is formulaic and identifiable. You can always spot a Ross style mountain or tree. And crunched-on foliage just doesn't look very convincing.
Use a stiff brush to apply the initial layer and a soft brush to apply subsequent layers. This makes thinning the paint sometimes unnecessary, and oily or runny paint is your enemy. The paint that is being painted over should be as dry as possible. That's where a stiff brush helps. You can scrub the paint around and keep the layer thin. Thinning the paint is unavoidable if using a liner brush, so that should be the last step. It isn't possible to overpaint such runny paint without ruining your work. Think about peanut butter and jelly. You can spread jelly over peanut butter, but not peanut butter over jelly. Wet in wet oil painting is exactly the same.
Light colors and highlights should be thick thick thick. The brightest highlights should be done last with thick paint in order to stand out. If a light color doesn't have enough brightness, darken the surrounding area. Paint can't achieve the value spectrum that our eyes see, so you have to fake it with contrast. Also, highlights are rarely pure bright white. They usually have a color and are often not as bright as you might think. Sometimes the highlight color is unexpected. A nice highlight color for black hair or fur is light blue. Reflected light on tree bark at sunset can be lavender.
Make colors more realistic by dulling the saturation with compliments and avoid white whenever possible. Start your mix with a light color and darken it instead of starting dark and adding white. Also, lighten your mix with a color that is lighter than the mix instead of white. For example, lighten red with cad orange and it doesn't become pink. Or lighten blue or green with cobalt teal. Yellow is a good color for lightening if the desired color is warm. Use white to make it cooler. Too much titanium white kills vibrancy and makes the color chalky. Don't think of green as just blue and yellow. Far more convincing foliage greens can be mixed by adding a touch of red or red oxide, or by mixing black or paynes gray and yellow.
If you use modern organic staining pigments, don't overuse the titanium white! Kill the saturation with a compliment instead of white or you will get chalky lifeless colors.
You don't need to use huge brushes! Many teachers emphasize that to get a "painterly" result, you must use a brush so large it makes you uncomfortable. This is absolutely not true. Those youtube alla prima artists whose paintings are chock full of gorgeous detail are not using big brushes. They're using whatever size gets the result they desire. Use whatever size you want. Period.
