Make sure that you do any modifications to the frame that you were planning on, because it's hard to fix the paint on powdercoat once it's done. Powdercoating works extremely well in most applications, unless the surface prep is insufficient. It also has a problem with chemically hostile environments (in some cases). I personally was going to use powdercoat until I heard of POR15. I plan to go with that when I get to that step (not finished with the frame mods yet). Other people might suggest that you use Zero-Rust or another rust inhibitor.
In reality, you can use anything that you want to paint the frame, as long as you prep it well. Most paints these days are very durable, even in a situation like frame paint.
Powdercoating is a pretty good solution, and if you make a volume deal with you local powdercoater, you can get a lot of your parts powdercoated at the same time, as long as they are all the same color. It's easier/cheaper for them to do a single color run than multiple colors. They typically reserve days of the week for different color types (2 days for black, 1 day for white, 1 day for red), to keep from contaminating other paint jobs, and to keep from cleaning the equipment all the time.
