Instead of putting WD40 on the threads of the bolt, before you put it in the wet epoxy (to cast in the treads), I have tried a different tack since I didn't know what the WD40 would do to the epoxy. I would rub a little oil
(from my face, since I sweat a lot in the sun) on the bolt threads, and then put a thin layer of spray paint
on the bolt threads with Krylon or some other cheap paint
. After that dried completely, then I'd put the bolts in the wet epoxy. After the epoxy set, the bolts could be backed out very cleanly.