Old style bare knuckles boxers used to use a mixture of salt and vinegar to toughen the skin on the knuckles and areas of the face prone to cuts.
Here are some other tricks:
Zinc oxide - Homemade is best because most is packed in petrolium based oils that dont penetrate and clog the pores. Can be had at pharmacists in powder form and made into a cream.
Tannic acid: Full strength is used in rust proofing metals. I dont know how strong you can use on skin, but diluted with water or vinegar and a small amount of salt might work pretty well. Probably best to heat it and soak the fingers in a small amount of it.
Benzoin: This is found in the health section of supermarkets. Its a tincture that leaves a sticky residue that is usually covered with a bandage. It also leaves a protective coating for abrasions.
It doesnt take very long to see tougher skin.
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