ive never had rattle can get baked off the valve covers.
that said, any decent paint will work.
if you want to clear them, for the best results, is to spray the VC in a gun, not rattle can.
takes longer, but turns out better.
i just used some rattle can clear on some small pieces iof this 59 GMC, and they look like cheap paint.
paint them just like you would paint the truck.
ive even sprayed rustolium cut with acetone, and its done fine.