You already know about making sure there's no residual amine blush before adding more epoxy, so I won't mention that ... but you know, subsequent coats of epoxy just need to have the shine removed from the previous coat (unless the prior coat is newer than 36 hours old, plus or minus). You can take the shine off, without removing epoxy that you want to keep, by just lightly scraping ridges, specks/bugs, bumps off first then put your random orbital on top of a green scrubbie and 'sand' the epoxy. The random orbital sander does a great job of scrubbing epoxy with a green scrubbie ... takes the shine right off without actually sanding. Folks not using peel ply may have more of a weave pattern left that needs to be filled, so sanding helps ... green scrubbies alone may require more fill coats to get it all smooth (MY opinion is that the only smooth, shiny, faired surfaces should be those between the waterline and sheer, the exterior faces of side panels, and maybe the roof of the cuddy ... all else is OK to see a fiberglass pattern on).
Brian