I just tried out an inexpensive product that seems to work very well and thought I'd pass it on. Although I row a lot and have the calluses etc. I was getting sore hands. Not sure the exact cause but I must move my hands on the c2 blue handle and create a lot of heat and friction. I found this site on the net http://www.newgrip.com/rowing.html and got just a pair of "Power Pads", not the ones with the wrist strap. Basically just a piece of neoprene with an elastic band across the back. No more sore hands and after about 100K no signs of wear. $10. well spent for me.
btw-I have no connection whatsoever with the company etc.
Jim