When I sprayed my rear rim I took the wheel apart, cleaned the rim as good as I could. I wanted a matt black look so just got some matt black from Halfords and just sprayed it like that. It looks great to me, no need for laquer or the rest to be honest. Maby with frames but for rims I would just say spray it.
I know this is my way an other people will differ. Thats just how I like to do it.