Search online for Golfer’s grip tape. The nice thing is you can tear it with your fingers. The only thing I find about taping your fingers is that this tends to rip holes in over-grips pretty quickly. I now use them with just a leather grip and no overgrip. I wouldn’t use them at all but the callouses on my thumb sometimes crack and get a bit sore. No problem with the tape.
Not sure if your fingers are your target points, or your palm... but I've got arthritis and sometimes gripping the racquet is rather uncomfortable, so I've found that simple bandaids work for me.
I apply the padded part of the bandaid to the inside fatty part of two of my fingers... two bandaids on each finger - one above and one below the main knuckle. It's not much padding really, but for me it makes a surprisingly good difference. Serves were especially bothersome, but the bandaids really help for me. Throw a bunch in my bag, easy to apply, cheap, all good.
I play agood amount, 4-6/week
only times I notice calluses and blisters is when I play too long with the same overgrip for too long
when i change overgrip every week or so I don't notice the calluses and blisters
I see people who play as much as me to maybe less, who suffer from calluses,,
but maybe my affinity to changing to a clean grip more often, has helped me with this issue
by using old/dirty grips for too long, you have to naturally grip harder, so the racquet wont slip out of your hands