Jim:
The Kirker Enduro I mentioned sands out pretty well. I am unsure how deep the pits are, but I would fill them with bondo, either before or after the epoxy if the epoxy alone is not enough to fill them. If you want to fill them after the epoxy, sand the epoxy first (80 or so grit) so the filler has some "tooth" to hold onto to.
Any areas that you use the Ospho on, should be at least primed afterward. The Ospho doesn't stop the rust if moisture gets to it. Therefore, something like the epoxy is necessary to seal it up from moisture afterward. Also, body shop supply places sell something called a cavity wax for applying to areas like you thinking of. You can look into that as well.
I hope this helps.
Regards,
Steve Lorio
New Orleans
