I recommend:
- Setting the rivets flush or slightly below flush.
- Skim coat of micro over the rivet line, let it set then sand.
- A bid of glass over the rivet line, perhaps 1” or a little wider.
- After set, another skim coat of micro, then sand with a long board. This is done when you are ready to final sand all your cowl body work.
Reason - if you just use micro (or some other filler) without the glass over the rivet heads they will eventually pop just enough to ruin the paint.
Carl