When I had an increasingly stiff pedal (only thing that gets increasingly stiff as I get older
), I pulled the trans and found that clutch dust had dirtied up the little bit of grease on inside diameter of the throw out bearing to the point that there simply was no lubrication going on there anymore.
There is a small groove inside the throw out that is meant to be filled with a high temp bearing grease to help the bearing slide up and down the tube around the input shaft. I learned all this stuff from Brad Mayeur, BTW. Greased it as Brad suggested, and it has been smooth ever since, even with a stiff KEP pressure plate.