I've tried many ways to fix blisters and heal calluses. And, no, I refuse to pee on my hands.
Try this. It works.
Before you go to bed at night:
1: Take a vitamin E capsule or two, tear the end.
2: Squeeze, generously, on calluses and gentle rub in.
Hey Presto, hard hands the next day.
If it is a very big full blister, poke it near the base with a sterilizer needle. Follow steps above.
If not so big, then just smear it vitamin E.
Note: Vitamin E creme doesn't work. Use a capsule.
PS: I row. I know about torn hands.