OK lets see now? In my opinion, because I don't like etch primer at all, you should sand all of that off before spreading filler. Then spray the bare metal with epoxy before you do the filler work, it's my understanding that the epoxy under the filler actually increases the adhesion of the filler. Remember, you can apply filler over non-sanded epoxy if you do it in time (a week or more in some cases, check the Data sheet on the epoxy you choose). Then re-coat the panel with epoxy after your done with filler work, to seal exposed metal, and then prime with urethane primer. I have a 68 Mustang in the shop I've been working on this week. It was sand-blasted and had a thick coat of etch primer on it, before it came to the shop. I've been sanding it all off panel by panel, before I do the body work. The reason for this is, I personally don't trust the adhesion of the etch primer, especially when someone else put it on. Etch primer is an acid based product that must flash for a while before you prime it, and it's not uncommon for paint staff to neglect this in our go-go-go atmosphere. Acid remaining in the etch primer can effect the integrity of the primer put over it. Epoxy has the same down-side you need to let it flash a while before priming over it too. But, epoxy has adhesion qualities that are far better than acid etch. So, anyway, it's not really the easy way, and probably not what you wanted to hear, but (in my opinion) it's the way to do it right!