If you are going to paint it, be careful with using too many different products...I assume you want to use the Sea Going because you have some and the holes and whatnot are on the bottom?
This stuff is strong and an absolute bitch to sand with any precision..
Depending on what you are working on, I would use standard resins (either epoxy or polyester) and mix in some Cab-O-Sil (finely ground glass) and make your own filler. Much easier to sand and easier to feather out the parting line.
http://www.tapplastics.com/shop/product.php?pid=44Good luck...Keep in mind, any repairs made to fiberglass that will be painted over need to be primed and blocked several times and allow time for shrinkage to stop...(a couple weeks normally works) I have used Feather Fill poly primer before, works good and has a lot of fillers in it, so it blocks out baby butt smooth without a lot of fuss.
http://www.evercoat.com/productDetail.aspx?pID=70If in California, you need the Feather Fill G2.....California sucks ass...

GT