I use my JD 790 for the same things. I went to a loggers supply store and bought a cable that makes this easy. First, I put a clevis hook on my draw bar. The cable I bought (sorry I don't know the name of the cable arrangement) was originally designed for the cable skidders loggers use to drag logs up or down hillsides. I put the clevis hook thru one end of the cable (there a roundish opening in a steel eye kind of arrangement on that end of the cable). The other end has a sliding piece that adjusts basically anywhere along the length of the cable. On the other of the cable there is a steel collar that will fit into the sliding piece. It is all arranged so that you take a loop around the log with the cable and then insert the steel collar end into the slider. THen you use your 3ph to lift the end of the log up. I think I spend about $16 dollars for the ready made cable and it works like a charm. When I'm skidding smaller logs I sometimes have to take two loops around the trunk with the cable to make it short enough for the 3ph to be able to lift it.
My little 790 skids some logs that you wouldn't think it would skid as easily as it does. You just want to be careful to keep the log end as low as you can while still having it off the ground enough to clear obstructions. Also, drive slow while skidding. With any speed, it would be very unfunny to get the butt end of that log jammed into a tree trunk or something. Would bring you a stop in a rather unpleasant way.
But, a tractor makes a great skidder as long as you use some common sense about the slopes you're working on and the terrain your skidding across.
Hope this helps.
Steve Wells