I've dealt with hull blisters and have finally decided that they are
normally no big deal. I have never heard of hull failure from them
and they seem to be simply a cosmetic problem. As far as drag goes,
my fixed prop causes more drag. However, some ppl really hate em and
go so far as to PEEEEEEEEELLLL their gelcoat (sounds really painful)
dry the matting and re-gelcoat. I call this the Peel 'n Pray method
cuz most offen the blisters return. Its just too hard to remove all
the water from the matting even with heaters n such.
Once, I took an electric heat gun and applied it about 4" from a
blister (through the gelcoat)and was amazed at how much water came out
of the blister (This was after 2 months of drying). Clearly, passive
drying dont work.

SO: Useless idea #3727

Peel only in narrow strips in a grid pattern to allow moisture to exit
and apply heat to the grid squares. However, heating the glass is
inefficient when you really want to heat the water. Instead, use
microwaves which couple to polar molecules such as water and dont
couple too well to the glass or resin (ie, you only heat the water).
You could measure the microwave intensity inside the boat at different
places as a function of time to determine dryness. The moisture would
attenuate the waves and a dry hull would not.