Ive used Apple Barrel. Best results were using Windex to thin. Believe me, I tried every darn thing. For me, I found that upping the pressure for my A/B to 35 lbs, thinning the paint what seemed like WAY too much, and laying down multiple ( think 10 very thin coats ) gave me a quite smooth finish, with none of the buildup enamel or even lacquer has. I think its experimenting, and finding what you like. The MOST important thing is to have the paint and your thinning medium EXTREMELY mixed, way more than waht you might do with enamel/lacquer.