I have been working on a handful of plug kits from mike, used helmsman on the majority, then used devcon on 1 of them, and the devcon came out really good. can i use the devcon over the helmsman or will it not take? I dont want to sand off the helmsman because im sure i will lose some paint. Will a scuff job do the trick? thanks guys...

ya, just scuff so it has a bite
I'd wait long enough to be sure it's good and cured.