Bob;
I'm wondering how old is the barrier coat under the exsisting bottom paint ? Could be it's old and needs to be replaced. Once the barrier coat is compromised, blisters can be quite common. If such is the case, you'll have to take it all the way down to the fiber glass and re-apply a barrier coat before applying another coat of bottom paint. Happened to an old Pearson 365  I had.
 If such is the case there are several solutions. Some folks here call in a sand blasting company and they'll sand blast the bottom ($1500.00 here in SW-FL) or get some folks to hand sand it all off. ($1500.00)
Barrier coating dries quickly and you can get 5 coats on in a weekend. Then the bottom paint. The folks up at Jamestown Distributors were good to talk with rgarding the process. It's all in the preperation.

Robert,

I am not an expert, but here is what I would do:

1. Open all the blisters to start drying them out
2. Remove all bottom paint by sanding or soda blasting
3. Wait until blisters are dry.  Not sure how long this would be, but I think a few days minimum.
4. Fill in blisters with West System epoxy thickened with colloidal silica.  Here is an article: http://www.boatus.com/magazine/2013/june/hull-rx-when-and-how-to-repair-gelcoat-blisters.asp(link is external)
5. Apply epoxy barrier coat per Bob's suggestion
6. Paint with bottom paint of your choice

I have hull 1384 same year as you and don't have problems with blisters.  I am in salt water.  My understanding is boats in fresh water are more susceptible, so perhaps the salinity changed where you keep your boat.

Good luck,

Ron St. Onge
Catalina 36 MKII Hull 1384