I just ran into this product by accident, but it seems to be possibly the most effective and safe way to prevent blisters. This substance called "Blister Shield" which comes in liquid roll-on, and powder form is made for athletes, but I believe it extends perfectly to us bass players. I only had the powder so far but I applied small amounts to my fingertips, and it seemed to drastically reduce the friction between my finger and the string, without any drag at all. My fingers are pretty callused so its tough for me to judge the effectiveness, but maybe you all could be better judges? Seems like a perfect product for bass players.
Blister Shield
