After drilling, I place white Duck tape over the inside and outside of the hole. Then I drill a tiny hole in the tape at the most vertical aspect of the drilled hole and inject thickened epoxy with a 5cc syringe (most pharmacies will give you a half dozen free.) Then place another piece of tape over the small hole to keep the epoxy from escaping.
It isn't a bad idea to wet any exposed wooden core
with unthickened epoxy with a Q tip first to seal the core
, but it's probably unnecessary and will likely be messy.
Read Mainesail's articles on drilling and filling. Note that you only drill as large a hole as you need for the hardware
, then remove an extra ream of core with a dremel tool, keeping the outer fiberglass
skin intact which provides extra strength. Also, when sealing use butyl tape as he directs (and sells) after chamfering the edge to get a good butyl seal.