I used The West System. They have a great book devoted to blister repair, and have years of research in epoxy development. The book also was very helpful in estimating supplies, etc. After allowing the hull to dry all winter (December through March), I began the fill job. Sure enough, just as the book indicated, each of the voids had developed very small "pin holes" indicating a dry hull. Scrubbing down the hull with a stiff wet brush also ensured all dust was removed from any of the pin holes. Once dry, I began mixing epoxy. I used a fast drying hardner (205) due to the cold temps here in Vermont in Spring. Each void is first "painted" with un-thickned epoxy, to ensure each pin hole is filled. Once tacky and able to support additional coat you start to fill. I worked with about 3-4 pumps each (Epoxy 105 and Hardner 205) and then added 207 filler until something between a "mayonaise" and "peanut butter" consistancy was reached. Too thin and it ran. Too thick and it didn't spread out smoothly. For larger voids, some microfibers were also added to the mix. I found I couldn't get rid of batches fast enough that were larger than 3-4 pumps. Spread your batch of thickened epoxy over a cardboard box top. The thinner you spread it, the more time you have to work with it before it hardens. I found the spreaders offered by West System were just the right stiffness to spread the epoxy nicely yet firmly. Work fast to slap your epoxy up there before it starts to cure. This is just like dry wall work. No difference. Be carefull not to.....spread too firmly. This causes a depression in the center of the void, forcing extra coats. Ramp up your epoxy towrd the center of the void. This ensures it's completely full. I ended up having to do at least 2 coats to each blister. Some needed more. This had much to do with how the first fill coat went on. If pin holes emerged once dry, you have to fill them with a thin coat of less-thickened epoxy. If upon sanding...you sand to much (WHOOOPS!) ya got to go back and do another coat of epoxy, etc.. It was a long process, but one made longer with the learning curve. The attached photo.....is of the hull with filled voids waiting to be sanded. Next episode.... Sand that hull fare! Kevin in VT