I use the Edge Pro Apex and while I sharpen at the lower grits of 120 up to about 320, I can feel the burr pretty easily with my fingers. I just use my fingers and glide down along the blade perpendicular to the edge. But as I go to up to 1000 and sometimes even 600, I find it increasingly difficult to feel the burr as I sharpen. Even when I go many passes on one side, I sometimes still can't feel the burr on the other side. I've tried on super cheap 10 dollar knives with super soft steel and I'm able to feel it there, but when I sharpen my S35vn and M390, it becomes super difficult to feel. I know that it's not a difference in the stone thickness since I use the stop collar to ensure consistency among different stones. And I don't think it's because my fingers are are too calloused either. In fact, they aren't calloused at all. Does anyone have any tips on feeling for the burr as the burr gets smaller as you go up in grit?