Depending on the steepness of the beach, you might be able to use the following approach.
After seven years of moving my Mystere 6.0 up and down the beaches on Southern Califnornia's Channel Islands, I have come up with a very simple method that can sometimes be done with one person. I'll explain, then I'll explain the system that Bill Mattson and myself use for more difficult situations.
With the bows facing downhill, place a pair of fenders
like these under the sterns. Wrap your arms around a bow and lift the boat. Most of the weight transfers back to the fender rollers and you just might be able to shove her uphill.
Here's how Bill and I do it on remote islands where nobody is around to help:
We use what we call Q-tip rollers that are a pair of fenders connected together by bungie tension and spaced apart by a section of ABS pipe. We carry two or three sets. With those under the boat, we plant an eight pound anchor in the beach and pile boulders on top of it. From that anchor we rig a 4:1 block and tackle to a bridle rope tied to the boat's cross beam. One guy pulls on the block and tackle, one guy pushes or pulls the boat and rotates the rollers as they pass under the boat.
You could replace the anchor with either an existing tree, or a steel survey stake that you sledge hammer into the ground. Or you could burry a 4"x4" post.
Bill demonstrates moving his Hobie 18 by himself. GARY