I used autofocus with the primary of Edge and it works well. Here are the main things to set up:
Make sure the focuser is turning counter clockwise as the focus numbers go from high to low. SGP only takes autofocus curves from high to low - and you want the direction to be CCW so it is pushing on the mirror.
Once you have that set, enter a backlash value that is at least about half a turn of the knob. This will depend on step size. SGP will let you set the backlash compensation so that it kicks in when you need to turn the focuser clockwise (to higher numbers).
Once the above two things are set you will find that changing focus clockwise will take much longer because it will overshoot and then come back ccw. But as long as you always take out backlash that way, the system should end up in a stable focus position and things will be repeatable.
Now you can use frame/focus and short exposures to find focus manually - by starting from high numbers and stepping down until the stars are small. At that point you can try an autofocus curve with about 9 steps. The step size should not be too bit or two small. Ideally it will trace out a curve that has a good shape and isn't too steep or flat.
I use a C filter and exposures of 2 seconds for my system.
Doing autofocus will involve long periods where nothing is happening because backlash is unwinding. And at the end of the autofocus process it will sit there saying 'complete' when in fact it is still unwinding backlash and coming back to focus.
Oh - and set the minimum star size to a small number like 2 at first - to make sure you are measuring all stars near focus. Then increase it later if it is picking up noise instead of stars.
Frank