Paul,
The Rustoleum will go over butyrate just fine as long as it is gassed off at least several days and has no smell. One thing with the Rustoleum, spray it on in light coats hold the can about 12" off the surface, do a dust coat let sit 3 - 5 minutes then do another to fill in. If still not full coverage wait 5 minutes to do another light coat. Rustoleum will fuzz up if it goes on to thick. If it does fuzz up, let it dry three days. Sand it down first with 220 paper then finish with 400. Make sure you tack rag off all the dust, then start again. If after these coats you think you need more wait three days before repeating for more coverage. I have always gotten full coverage by the second light coat
Once you start with Rustoleum you are committed as you cannot apply any type of dope or acrylic lacquer (Primer, Krylon, LusterKote) over the Rustoleum, I tried it does not stick an crazies as it dries and shrinks.
Best, DennisT