It's not a Glock is it? Those things rubbed my finger bad, too.
I don't use gloves to shoot. I figure if I really need to shoot the gun I won't have gloves on anyway, so shooting to protect myself would be "different" than shooting the pistol any other time.
And, my dad would grin and say that if you're getting a sore/blister then you need to toughen up by doing whatever it is that makes your finger/hand sore more often. I can agree with that, when it comes to shooting.
Any chance of modifying the grip so it doesn't rub? I removed some plastic from the bottom of the trigger guard on the Glock and it helped a little. The GFA helped some more. It still doesn't shoot as good as my CZs though.