ah, ok, cheers guys. I put the primer on first thinking it would be easier to remove the paint from the foil. Laying the foil on just before the last coat of paint sounds better, thanks Steven. The foil I used is just regular kitchen foil, very thin. It's not bacofoil, that stuff is much thicker. To give an idea, the kitchen foil is thinner than bacofoil, and bacofoil is thinner than the chrome ducting tape I use for trim. I see no difference between branded BMF and regular kitchen foil apart from having to add the adhesive yourself. I'll clean off the area and place the foil on just before the last coat of paint.