For what it is worth, . . . Resolene works fine without an air brush if you first thin it 50% with water. I use a 1 inch camel hair brush (el cheapo at that) and I keep working on the piece until the bubbles are very small.
Normally, I can do an IWB holster (inside and out) in about 10 minutes.
I do my finishing just off my wife's kitchen, . . . so spraying is not an option for me, . . . and I am very happy with the results I have gotten using this system.
I only have had one bad experience with Resolene, . . . it was on an oil based stain I was trying, . . . and the project turned very dark for some reason. It was my only unexpected result, . . . but the customer was OK with the color so it worked.
Normally, I use a solvent based dye, vs. oil base, . . . and the colors are rendered true under the brushing of the 50/50 Resolene mixture.
May God bless,
Dwight