I can’t quite figure out how to get a smooth finish when airbrushing neon paint colors. I feel that I have properly thinned my paint but still seem to get darker areas in crevices. Can someone explain how to get a nice even neon paint job?
Not just neon or dayglow colors, but any light colors, it helps to start with corners or crevices, then work outward to larger surfaces. It’s sort of counterintuitive, but it really helps limit that kind of buildup in the recessed areas 
If you are getting darker areas in low spots there are two things you should look at. It could be one or both of these things.
- Your paint is too thin. If your paint is too thin it will naturally run down into the low spot.
- You are applying too much paint in each coat.
You could start by leaving your paint as it is and try addressing the second one. To apply a lighter coat you might need to shoot from farther away, or move the airbrush faster. Remember if these paints are very light or very bright you are necessarly going to see your first 1 or 2 coats of paint.
I would start there. Apply your coats very light. It doesn’t matter if you need 10 coats of paint as long as you get equal coverage.