Having done an extensive blister repair and barrier coat on An '84 San Juan
28, I used West epoxy for the blister repairs
using their high density, low density and colloidal silica fillers (depending on how much damage was in each blister). Plus fibreglass cloth in some cases. When they were all fixed and faired, I used Interlux
Interprotect 2000E for the REQUIRED 5 coats. I considered West epoxy with the barrier additive but for ease of use for a big job Interprotect 2000e was much easier to do, you just mix the two cans together and away you go. I had the boat for five years after that and had no reoccurrence of blisters
. I now have an '86 C&C
33 that had an extensive bottom peel, epoxy re-glassing and five coats of Interprotect, no issues to date.
If it is a small repair, I'd go with West epoxy + their additive ( 422? ). If it is a whole bottom, Interprotect 2000e, just for ease of use if nothing else. They are both excellent products.