Soft between the straps part 2

I've got a small area that is soft between the straps and want to patch it up. I want to try injecting foam as per http://www.boardlady.com/injection.htm. Trouble is, what product do I use? I went to the hardware and they had the aerosol cans of foam used in the building industry and I went to the local boat factory and they had a 2 part urethane but I was advised that it got hot when it cured and may melt the existing foam base. This may have been because they use a much larger quantity than what I will be using, maybe not. Is there a company name or a product name that someone else has used and been successful?
Another question, after the foam is injected, what do you do with the holes that remain? Epoxy over small squares of fibreglass?

Dunno what product they were referring to but the PU's I have used don't get hot even when very confined

Erathane 450 is the go - but hard to find. Their 330 is most common and cheaper (it replaces the GP2 so that will do if you see it but any GP2 still around will be old so ask for half price). (ERA Polymers).

make sure u mask well, the excess foam on the deck will NOT come off
buy a 50ml syringe or 5, it is worth it cos u have to work FAST

After you're done and cut the excess off - in the the holes rebate slightly with a drill bit BY HAND about 3-5mm deep then poke in 2 or 3 layers 4oz glass wet out with epoxy so u make little "cups", then a drop or two of epoxy / q-cell mix to fill the last little bit

EDIT - don't even think about the single pack cans from hardware it is crap