To calculate the focuser setting, CFZ is calculated from the distance the tube moves in one rotation of the focus knob and the F value of the optics.
You need to have about 10 steps within the CFZ distance to get a precise focuser setting.
I used the "Myfocuserpro" document as a reference.
If Crayford Focuser has a fine knob, 28BYJ-48 might work.
In any case, you need to find the required number of steps from CFZ.