I really am a fan of lecithin for this.
With my DD I had a recurring blister for around 2 months! It would pop, dry, heal then just reappear like it had never been gone - until I started eating a ton of eggs (a natural source of lecithin) every morning! Ok, not a ton, but 3-4. After being on the eggs, it popped and healed one last time and didn't come back.
Good luck! I know first hand they hurt!