Prepping Bumper for paint.

Going to do the same thing and what I found was 60 grit then 360 grit to.Although that seems a bit aggressive you have to get deep cuts to get the primer to hold to chrome.I plan the use high build primer after the self etching primer then sand smooth before paint to make sure all the scratches are covered.I'm no expert that's just what I found by searching around and it seemed to be a pretty common technique.