Seth --
What do you man by 'wax'? are you referring to the wax surface that develops when using air inhibited polyester resins ?????????? ..................... and do you or have you found zones of air inhibiting wax in/on the bulkhead panels you've already ripped? So, you need to clarify a bit more and whether you intend to use epoxy or polyester for your impending layup. If there "is" wax and you intend to use epoxy, then YES you must thoroughly remove the wax. GRINDING without dissolving will only smear the wax across the surface; you HAVE to use chemical means to remove it ... solvents, then a 'wax lifter' such as Interlux #202. If there *is wax* and you intend to use polyester resin, then SOMETIMES you must remove the wax .... but many times the air inhibiting wax will dissolve into the resin; so, you have to /should test to see if the wax dissolves into the resin (no MEK addition needed to do the test) .... just pour some resin onto a glass plate, put some scraped wax onto the wet resin and see if it dissolves completely, etc. Using polyester resin to add to a prior laid-up and cured polyester .... doesnt usually result in a very 'strong' bond once the original fully 'cures'........ .