I've suffered with easy blistering for years. My feet sweat heavily, and refuse to form callous, even after extended training hikes and climbs. If I don't change socks every few hours, I may even get 'trench foot' (painful skin breakdown with severe 'prune foot', like standing in bathwater for a few hours)! Thousands of dollars spent in the highest quality boots, insoles, tapes, etc. didn't help. I've now discovered something that's really helped out a lot. I still get squishy feet, but blistering has been rare, and much more superficial than the previous nasty, deep, blood blisters. They're called Bunga Pads (www.bungapads.com, I think), and no, I don't work for them or know them personally. They were invented for hockey, figure, and speed skaters, but work great for climbing and hiking. They are a polymer gelpad, bonded to an elastic sleeve that fits over the problem areas of your feet or toes. They make many different sizes and shapes, and aren't priced too badly. Eventually, the pad will delaminate from the sleeve, but they should last you at least a season or 2. They've really made me enjoy tele skiing a lot more. Last thing I can think of trying is to get Botox (butulinum toxin)injections to the skin of your feet. It will kill off sweat gland activity for 4 to 6 months at a time, but costs a fortune, and not covered by insurance, of course. Think I'll hold off on that one! Good luck.
-David