If you plan on removing the foam plug from your hull, you'll definitely need something to give you a nice surface to release from, like Steve Collins says. I've had good luck with duct tape in the past. Yes, it works fine; just make sure you layer it a bit so the tape covers all of the foam; the slight bump you get from the overlapping tape won't show after a couple layers of cloth, and the plug pulls out cleanly leaving a nice clean inner surface.

Also, make sure you control the temperature of the area you're working in; no working in direct sunlight or that sort of thing...