How do I prevent the skin on my feet from getting extremely bad calluses?

I play tennis 5.5-7 hrs a day and I have soft feet so when I sweat a lot my feet get wet and hot and I am also banging on my feet lots because of the intense tennis. I have nice shoes that help and I sometimes even switch my socks in between matches and such but I usually dont have enough time to walk around in flip flops to air out my feet. It is hard because the courts get hot and there is nothing I can do when my feet start hurting in the middle of a point. Also, last year I played about 2-3 hrs a day and I was good to my feet like I am now but I got giant calluses that tore away at my heel and front sole. Like literally a good layer of the cushy part of my foot peeled off. I am very worried because I Have only been player for 2.5 week this summer and they are already starting to hurt a lot! Does anyone know anything I could put on them or do to help them??? I am basically always barefoot too when I am not playing tennis