Rust Shield or Epoxy primer
 

Hi,

My engine bay and wheel well is taken down to bare metal. Would you recommend Set Rust Shield or Epoxy primer before Gravitex?

personally I would do the epoxy primer for something like that.
SEM rust shield is a DTM and top coat all in one and you don't need a top coat under a stone/chip guard. the primer will offer an excellent metal protection it will dry faster so you can scuff it with a red pad and apply your stone / chip guard depending on what epoxy primer your looking to use you maybe able to even go wet on wet from your epoxy primer to your stone / chip guard this would save you time and labor if you can do this. if your thinking of doing wet on wet check your TDS to be sure you can.

I just did my entire car last week. Used rm epoxy 2 coats, then gravitex. I let epoxy sit for an hour then hit it with gravitex. As 962 said if you let epoxy dry too long you’ll have to scuff the entire thing.