you would use a etch primer on the bare metal that is what etching is. then you can hit it with a high fill primer.
When you prepare primer for top coat you should block it back with 180 grit dry sand paper to remove the peal, then 320 dry to remove the 180 scratches, then finish with 600 or 800 g wet and dry for the final coat.
I usual use a very week paint mix to make a guide coat which i wipe on with a clean rag this will show all the sanding scratches and highs and lows