I'm sorry but I have to disagree. Most pros, when doing bodywork after an area has been stripped will recommend using a good epoxy (two part) primer to seal the surface first. Body filler is porous and will attract moisture which, if not sealed out eventually promote rust. Not that it won't work without the primer but to ensure good results, especially if the bare metal has been sitting for even a few days, it's a good idea to seal it first.
After the body work you should use a good sandable primer, not epoxy, it's too hard.