MC,
I think you need to start as Ty suggested by first sanding down the bubbles and get it smooth. Then hit it with primer sand smooth. Then do a coat of two to clear butyrate Sig lite coat (this is non-shrink). Then go to color with Sig butyrate (this is also non-shrink). In hard corners I use fillets (fuse/wing joints, stab/fuse, rudder/fuse. I like micro balloons and finishing resin mixed very thick.
Best, DennisT