Do they have the blister pad band-aids at any of the gift shops? Those might help. You may have to double up on them to increase the padding. Unfortunately, I don't think there is anywhere you can get it at WDW and you already have blisters, but rubbing Body Glide all over your feet in the mornings before you head out to the parks will prevent blisters. I got blisters every Disney trip until I started using it, and since I learning about it, I have never had a blister at Disney again. If you can get stick deodorant in the shops, you can try using that like Body Glide-- I have heard that can help. It might help keep you from getting blisters in other areas with different shows.
To speed up the going away process, neosporin? That is pretty much all I can think of. I've heard a warm water soak might help also.