I've done the same thing with my trailer sailer and I just don't worry about scratches and dings. Someday, when I'm done hitting rocks and piers, I'll redo the topsides.
You could, however, lay a stern
anchor as you approach the beach and
cleat it off just before hitting the sand. Then take a second
anchor ashore (or drive a stake in the sand) and secure the boat from bow and stern.
Before you retire for the night, pay off the beach
anchor and draw in the stern
anchor moving the boat into deeper water.