What I do is just attach the bottom links to the attachment, make sure the attachment is straight with the tractor and as level with the tractor as you can make it. For each of my attachments I have a rope with loops on the ends. Using the unattached top link of the attachment put one end of the rope thru the pin, then around the PTO shaft then thru the pin. Now the heavy PTO shaft is being support by the attachment and not me, is level with the PTO shaft on the tractor and I am not hitting my head on the top link.
I put a piece of tape (or paint) on one of the curves of the attachment end of the PTO shaft. With the tractor OFF, I have no problem turning the PTO shaft by hand on the tractor to line up with the mark.