Hi-
I focus an sct with robofocus on the primary - so the mechanics are similar but the exact step size stuff won't be.
I use 9 steps and 2 second exposures with sct and ccd - and I have backlash compensation set to about a full turn clockwise of the primary focuser knob. I make sure the focus curve is taken from high numbers to low (right to left) while turning the focuser knob counter clockwise - and backlash compensation will kick in any time I need to go toward high numbers.
I hope the above makes sense because it applies to any system for focusing with the primary focuser knob.
The 9 steps provide a parabolic plot and not a sharp 'V' so that I can see the shape and width of the bottom of the curve. Opinions differ on that - but I like to see the true shape of the curve near focus.
Taking out a full turn of backlash may take some time - and you may be able to get away with less, like half a turn.
I would use an ISO that is pretty high but doesn't saturate the stars.
With a dslr you may be completely limited by the download time of the frames - so maybe 7 steps would be better.
I would use about 2" as the minimum star size - if you are sure your in-focus stars are not smaller than that. Use the pixel size in arc-seconds to find out how many pixels that is. You don't want to lose stars when out of focus because they are too big - or lose stars near focus because they are too small.
Hope this helps-
Frank