I spend a lot of time on auto body forums because right now I am working on the rear end (prior to that the frame) and I would say yes that would be okay. Evercoats Rage Gold is good over bare metal, etching, or epoxy primer. These bondo's do not specify each and every coating they work with.
The first thing I do with frames, rear/front ends, and misc parts is rough everything up to start using 80 grit, then coat everything with DPLF40 Epoxy Primer. I then fill all of the low spots with rage gold, then 220 grit and grind those things that the factory didn't clean off good, which means I am mostly back to bare metal, then re-epoxy over the bondo and at the same time (90 minutes dry time) use K36 Urethane primer with several coats. Once its primered with the high build urethane, I use 400 grit dry to finish it off. If there are pinholes or small low spots, I use a dab of polyester filler. Lastly, Sealer, then topcoat.
The disagreements between the professionals are:
1) whether to use etching primer first. The consensus on the forums I frequent is NO. Epoxy primer seals everything underneath very well and gives the very best adhesion characteristics available. But its an ongoing argument.
2) Going beyond 400 dry before topcoat. No need if you use sealer. Sealer is the great equalizer. You never sand sealer since it is put on at the same time as the topcoat. Since you cant sand the sealer, however you lay the sealer down, is how your topcoat will turn out. Sealer seals the scratches that 320 lays down completely, so 400 is insurance that your topcoat will be show quality pristine. If you go to 600 wet, its nice and all, but the sealer will dumb down your work. No need to go that far.
Of course, then there is wet sanding to smooth the orange peel or overspray issues once your topcoat or clearcoat is down.
That's the long version. Hope this helps. I have heard good things about Zero rust. If you aren't going down to the bare metal before paint, its probably a good choice.
