The first thing that comes to mind is gear....You could reduce the action on your strings. You could reduce the gauge of your strings. You could play electric guitar, instead of accoustic. Any or all of these gear changes could help your sore fingers.

You are on the right track regarding using a light touch on the frets. When you play, using a light touch on your fretting fingers, work on strumming softer as well. This could help you reduce the pressure needed for clean notes to sound. If you are working to hold the string down lightly and strumming hard... you could be working against your own best interests. Practice using a light touch with your pick.

I am sure you have heard this, but it is still important to keep in mind....Time practicing, is probably the best cure for sore fingers. At an hour every day should be enough to eventually you develop callous, and a light enough touch, to reduce the pain. I am sure, after "years of practice" that you already are seeing an improvement to how your fingers hold up to stustained practice. I bet you could not practice for an hour when you first started. That will continue to develop, if you keep at it.

If all else fails there are "practice gloves" that can help with using sore fingers. I have not used them but I have heard good things about them. Maybe that is another gear change that could help push those boundries you are running into at this point.

Hope this helps.