The link above would not open but it sounds like people are saying you can just open up the known blisters dry out and and then epoxy.
In my experience you should take off all of the gel coat and then dry the hull. There will be internal blisters trapped within the gel coat that have not appreared yet.
On a 22 ft boat it is not that big a job to remove it all. I just completed a 30 footer and that was fun.
I found a powerful ( 3 amps) random obital sander to be the best method.