I actually worked as a painter/powdercoater for a year. we mostly did high production stuff. The main problem with homebrew powdercoating is most people don't get the part hot enough for the powder to bake in. If you powdercoated something and it chips easily, than its not hot enough. If your doing parts that have thick metals it helps to pre-heat the part than spray it. Than when you bake it it'll stick better.
As for painting, its pretty easy. You'll be able to see if its too thick or too thin. IF its too thick you'll get an orange peel effect like regular paint. If its too thin than you'll be able to see through the powder. If your going to respray the part than turn down the voltage to 50 to 80%
The only pain in the ass part of powdercoating is when the spark arcs to the part or a contamination on the part causes the back corona effect (round circles where the powder is real thin and won't really stick). Make sure the part is clean and you'll avoid this problem.
Other than that, good luck