bassin,
Welcome to TU and your first post. A lot of knowledgeable people here that powder paint from using the brush (tap) method to guys that use a special airbrush for powder paint. As far as what kind of brush to use, I use nothing fancy. I bought a pack of 6 different size brushes at Menards that cost a whole whopping $2.00. I believe it had a #2 and a #1 brush in there which I use the most of. The most I'd spend is a dollar a brush. Just don't get it stuck on a painted jig, because then they are trash. PM me your e-mail and I'll send you a pic of what I use.