yes i sure will be carving some real ones. nothing beats the feeling of digging your hands into a pumpkins guts, like a zombie!
as for the spray paint, honestly i have only used my graffiti paint "ironlak" brand(love the way it smells plus very thick coverage).
since the pumpkin already has paint you really only gotta watch how you coat the inside, if you do the inside that is. i would say as long as you mist the first layer or so you shouldn't need to worry about it sticking or eating away.i would say store paint wise i would go with krylon plasticoat. Walmart .99 paint can be extremely watery and take many coats. krylon is good though.
as with "all" spray paint brands. it depends on the color as to actual opacity. in northern ohio krylon=$4.95 ironlak=$4.45, but you have to get it shipped out unless your lucky enough to live where there is a graf shop that carries it. i will saythough, with ironlakeven yellows take only a few coats everything else so far is super great
hope that helps in some way.
tip: with the inside what ever color you do it is what the "lighting" will show up as