I did one for a mate, i think i have some pics somewhere....
Firstly, you gotta sand and strip down the old paint (obviously before this take the thing apart)
Then use some decent primer, and throw on a few layers.
From here you have a perfect start for any design.
I used car spray paints btw.
Lastly make sure you lacquer it to sheeeeeeiitttee. Ths more lacquer the better.
The whole process takes about one to two months for a decent job. If you go ahed with it pm me and ill letyou know all our problems /findings and exactly how we did it to help