I have found an acrylic (latex) primer that can be wet sanded: Rust-oleum Painters' Touch Ultra Cover. BUT I could not get it to level, even adding Floetrol. It takes a lot of sanding to remove the brush marks.
From what I read, it seems that many water based coverings require new application techniques and conditions, and a higher humidity level may be required to get brushed wb coatings to level. Right now my shop humidity is running 60%, at 68 degrees, maybe humidity too low, and/or temperature too high, to achieve leveling.
Others may be able to use these wb acrylic (latex) primers, but I am going to try the wb epoxies. These have much longer dry times:
System3 wb-155 (which I think is the primer sold by Nelson's): Tack Free at 77 degrees F: 4 hours, Recoat Time at 77 degrees F: 12-24 hours, Full Cure Time at 77 degrees F: 7 days
System 3 silvertip yacht primer (a two component like wb-155), recoat when dry (about 30 mins), full cure 1 day.
With both products, System3 recommends 3 coats. With both products, you are instructed to let the product fully cure before applying topcoat; So you should wait 7 days from last coat of wb-155, or 1 day with silvertip primer.