Howdy. My focusser here
http://www.users.on.net/~josiah/focuser/IMG_9933.jpg
has 2 large knobs with knurling machined onto them for grip. I have a bit of wire attached over 1 of them them to act as a pointer, I will take a short image, and check star sizes using camera zoom function. I will then turn the focusser knob say, in 1 row of knurling on the knob by watching it move under my wire pointer. I will take another pic. If stars larger I turn knob opposite way twice as far (2 rows of knurling, approx 2 mm) then take another pic. Usually by 3 or 4 tries I have pretty good focus.
Scott