I have used spray foam insulation when doing holds, it was very easy:
http://greatstuff.dow.com/
I believe I used the red one. You install the holds then drill one hole in each so that you can fit the spray straw through. then you fill it up with the foam and the excess forces its way out the hole as it expands. then you can just cover the hole with glue or fiberglass and you're done.
mine were installed in maybe 03 and have not had any issues since then
the beauty of this is that there is no mixing or mess. you just toss the can when you are done.
this one one of the first things I did on my ski on my own (with my father when I was in my early 20s) it is a manageable job really, just make sure you have all the tools and equipment and go for it.