This is mostly for @Takran but maybe others will be interested as well!
#1 - Thin your paints!
This is critical when it comes to your minis or models having a nice smooth look.
Paint Brush - You want your paint to be no thicker than “melted ice cream”. You can go thinner, it just may require more coats. Play around with different viscosity to see what works best for you. Usually a little dollop of paint and a little water is all you need (tap is fine). See this video.
Airbush - You want your paint to have a milk-like consistency. If its too thick it will clog your brush then you’ll have to spend time cleaning it all out. I would suggest airbrush thinner over water because water will change the properties of your paint and can lead to adverse side affects. If you decide to go with water, use distilled so you aren’t shooting minerals and what not through your brush. See videos at the bottom.
#2 - "You’ll want to apply 2 thin coats."
If you watch any of the Warhammer TV tips/tutorials in the play list I put together you are going to hear this a million times. This mostly applies to paint brushes, but can apply to airbushing as well. It’s 10000000% worth taking the time to do two thin coats versus one thick coat. Always.
#3 - Quality paints (you get what you pay for)
Speaking of paint…I won’t advocate one brand over another, it is all personal preference. Try out different brands (Vallejo, Citadel, Army Painter, Testor, etc) just avoid bargain paints like Apple Barrel. You can use something like Apple Barrel acrylics, but you’ll have a harder time with it. I know the adage says “the artist makes the paint work for them” and that’s probably possible, but I prefer to keep things easy.
#4 - Brushes (get what you like, but take care of them)
For our purposes there are two types of brushes. Sable (natural) and Taklon (synthetic). There are pros and cons to both of them, the best way to find out is to test them out. You’ll want a few different types Taking care of your brushes is crucial or else you’ll be replacing them often. See these videos for more info.
#5 - The Wet Palette
I’m not sure what your house is like or what kind of weather you typically have, but where I live its dry af and any paint I leave on a palette is usually dry within a minute or two and thus wasted. In cases like this, a wet palette is a LIFE SAVER. You can buy a Masterson’s (look on amazon) wet palette or just make your own as seen here!
#6 - Have fun
Sounds stupid, but this can be a pretty fun and rewarding hobby so make sure you have fun while doing it.
Other helpful videos that I watch and re-watch!
Choosing an airbrush -
Airbrushing for Beginners -
Getting Started -
Games Workshop Painting Tutorials -
Games Workshop Tip of the Day -