yeah, you can use either bondo body filler or wood putty, either will work, sort of. that blue foam wont give you that terrific of a finish to begin with. I understand that its nice and quick to cut it with that wire, but I think youll learn that things can rarely be both nice and quick. Plus cutting it like that is bad for you and the environment.
If you try to spray paint it it will melt so make sure you cover it entirely with body filler, or wood putty, then sand it and coat it with a high build primer and sand it again, then do it over and over until you think its good to go and then sand it again, twice!