I think Bondo auto-filler is the best bet. I've used it several times and it's often recommended on the forum. It's available at Home Depot near the Caulking section. Drawback is that it STINKS and i think the fumes are dangerous My wife goes crazy when i use it because the garage is uninhabitable for a day or two.
Wood putty might be ok too, but i'm not sure how well it bonds to the primarily metal (screwhead) surface inside the divot. I've used it before but i can't remember how happy i was with it.
Last year i tried using drywall spackle after reading about it somewhere.... my goal was the same as yours, to get a nice smooth painted finish. DONT DO IT. It's far too fragile and after painting over it, i bumped a speaker when carrying it through a doorway and it dented the spackle under the paint and made a big ugly mess.