If you attempt this repair, you will need to wear proper safety glasses with side shields while opening up the blisters. Due to the osmotic nature of hull blisters, they are under great pressure and the water within the blister is acid (due to the chemical reaction).
If you keep your sailboat in the water for long periods of time and have not repaired the blisters, they will eventually penetrate into the fiberglass and cause glass and perhaps even structural damage. Most of the time blisters are due to poor fiberglass practice during manufacturing.
I have repaired a few blisters on a Ranger 22 (our very first racing sailboat). Like any fiberglass work, it was hard work but not very difficult. One of the problems is removing the paint. If you sand, you need to be careful not to remove the gelcoat within the surrounding areas. It is fairly expensive to sodablast but if you have several blisters, that will be the way to go.
S2 11.0A 36'