I dont know of any paint manufactor that suggests you apply filler over etch primer. In fact the beroxide in the filler's hardner can react with the etch primer causing the filler to lose adhesion.
Another thing is that sandblasted metal might have more tooth then what the etch primer can fill. Meaning even after you spray your etch primer you can have some spots of bare metal exposed because the etch primer can not fill that tooth left from the sand. Most manufactors want alteast 180 grit prior to etch primer.
Personally I would scuff that etch primer with a red scuff and apply two good coats of epoxy primer over that etch. Epoxy has far better adhesion and corrosion protection then etch primer. Plus epoxy primer is NOT PORUS like that etch primer. Etch primer can absorb moisture throu it, epoxy primer will not.
Plus you can apply filler over epoxy primer with NO PROBLEMS. Many car manufactors like Mecerdes Benz, Lexus and Madza recommend filler to be applied over epoxy primer.
An epoxy primer that would work with that etch primer would be PPG's DPLF line. But before you buy any epoxy make sure it can be applied over an etch primer as some can not, but DPLF can...Eric
