I sail an A-cat and launch and retrieve by myself all of the time. An A-cat being what it is, I never sail it up on the beach as I do not want to scratch my hulls (it is not good to sail any boat on to the beach if you want to maintain your hulls).

Go to West Marine and buy yourself a small folding anchor, about 20-30 feet of nylon line, and a 6"-12" styrofoam buoy. Before you launch, set your "mooring" buoy out in the water. After you get the boat in the water, tie off a bow with a bow line to the mooring buoy and take care of your dolly. Do the same when you come back in.