I have been grooming some of the singletrack up Cache Creek this winter and it is a bitch. It takes me over three hours to hike from the trailhead up to the fifth bridge and back. It isn't very far, perhaps three miles in one direction, but dragging the groomer is tough.
Just a four-foot kiddie sled clipped to a backpack. I put a 60 pound sandbag (contained in a stuffsack) in the sled and then rig up some chains to drag behind to help smooth out the trail and fill in postholes.
After three hours dragging this, I'm tired.