I just did my bottom with Interlux. It worked great. I had small bump like blisters I sanded flush with 60 grit and a 5" orbital sander. (Almost 5 hr on a 26'!) My "blisters" were more of a molding defect I think. They were about .5mm high and mostly just a dirt buildup. Nothing in them... solid.
Remember to wipe the bottom off with acetone after sanding and before applying the repairs.
Some photos of the crack, bumps, sanded, the Interlux, and the finished bottom (Aquaguard anti fouling), the patch 7x11"