Hi fellow guitarists, here are a couple of guitar playing tips you may be able to use...
Tips to help build callusses:
Rub your fingertips with (rubbing) alcohol ( usually found at the chemist) three (3) times a day for a week or two for a new player or a competant player who hasn't played for a while. This will dry out the skin and help calluses build very quickly. I also use it to clean my strings, Tape Heads, and guitar body.
Alum has a similar effect (again from the chemist) as it dries out the skin, good for mouth ulcers as well, wet your finger and dip in the Alum and put on ulcer, it stings but is worth it. but dont swallow it. A tablespoon in a cup of water will be fine for soaking fingers. Soak fingers for 15-30mins a day.
You can also use an old credit card to harden and maintain calluses. Hold the card across the palm of the hand and press each finger in turn into the opposite edge. You can do it anywhere of course. Even on the John.