For new boats , the best solution..
..is preventive epoxy barrier coated from anew.In our warm water , year around season , this is a standard procedure ,if done with high quality paints and procedure (next best thing is to have the boat out of the water for few months every year..).I did it on my 5 years old 29.5 , and so far no problems..Re this application , after blisters tratment , there are mixed oppinions. The new thinking is that , epoxy coating a previously blistered ( by osmosis , no due to badly antifouling painting..), might stop the inner small amount of liquids that are still present 'under skin' , from slowly 'migrating' out thru the gelcoat and antifouling paint to surounding water and eassing on the problem in future;if epoxy covered , they don't show outside, but accumulate nevertheless inside and cause more actual (and deeper) damage ,if way out is bloked;next time , there will be more blistering , and especially more work to remove the thick and hard epoxy barrier coat; all this since the now beleif is that unless hull dried and HEATED (professionaly , under controled and forced procedure and enviroment) in the repair proccess ,( and even this doesn't always succeed) the 'seeds' of osmosis remain underskin , to reaper in few years in other places..In this case local treatment of blisters only, and then antifouling , is the better solution (techical and financial..), to be redone probably every several years..But in severe case of blistering , when hull strenght might be lessened , epoxy treatment (and some fiberglass aplication too ) is needed antway.Still the best thing would be more perfect GRP manufacture procedures , both in materials and especially quality controlled work and enviroment.