I keep a bottle of spray on 2nd skin with me... I used to have the same problem with blistering. Right before one of my first real tournaments I practiced really hard and blistered up. The second skin saved me. It is in a small bottle, costs $5 bucks. Just spray it on, let it dry, spray it on again, layer it a few times and you wont even feel the blister anymore. I was actually bleeding before I tried this and it still worked.
I posted this exact question and this is the answer that worked best for me. I also have friends that use the "rob mares" style wrist band. That seems to help a lot too.
Now my wrist doesn't blister anymore because the skin has toughened up a bunch, but for your situation the spray on second skin is perfect. Practice away.