For context, I'm sixty-four, a beginner guitar player. Started lessons and playing regularly last summer. Playing two 2-hour jams per week and "try" to practice everyday. Some of this may be psychosomatic, but it seems to help for me. Here's what I do for sore fingers:
1) Stay hydrated.
I try to remember to drink more water, and keep a large glass of water nearby when I'm practicing or playing. Here in Colorado, the ambient humidity is around 27 percent. Things like fingers and guitars dry out quickly; even more so for older guys like me. With less water in the finger tissues, the string pressure on the finger calluses seem to irritate the tender underlying tissues more than when I've been drinking enough. I've also found that beer, wine, or liquor reduces the soreness, and adds a lot to my enjoyment of my playing. Unfortunately, it doesn't seem to improve my skill level; at least that's what my wife tells me.
2) Lightly sand finger tip calluses.
Once a week, or whenever I'm clipping my nails, I use an emery stick (fine grade) to lightly sand away some of the dead skin on my finger tips. Not much, just enough to smooth over some of the grooved edges that tend to catch on the strings. I do this in combination with number 3 below.
3) Rub a little dab of skin softener into the finger tips after playing. Not a lot, not every time, but several times a week I'll rub and work some skin softener into my finger tips. In combination with the occasional sanding, I've found that the calluses don't get as rigid and dried out, and thus don't seem to put as much pressure on the more tender underlying tissues.
I know these sound almost counter-intuitive, but they seem to work for me. And one more idea...
4) Just got back from a guitar lesson. My instructor suggested an exercise that helps to reduce sore fingers by reducing the amount of finger pressure applied to control strings. Position your hand to play any basic chord. For each finger, reduce the pressure on the string until you hear a buzzing sound; then slightly increase the pressure until the you again hear a clear tone. That's the optimum amount of pressure you need to apply to each string. He said the tendency (especially for beginners like me) is to really clamp down on a chord, and apply even more pressure after making a mistake.
I'm trying to teach myself to use less pressure on the strings, but honestly, it seems like every time I attempt to learn a new technique, or unlearn a bad habit, my playing goes to heck in a handcart. I keep telling myself that the goal is the journey of learning to play, but sometimes the "journey" sounds awfully painful to my ears!
Very much enjoy reading your posts, Welder. Thanks for sharing.
Best regards, Chris
PS - See Drguitar's post over in the calluses thread in this forum. Should have held up posting here until I read his post!