Spray the cradles with silicone (or McLube) and the boat will go on/off much easier. Even carpet scraps are slippery when sprayed with that stuff.

Most people use some sort of "bumpers" on the sterns when loading/unloading. John Bauldry makes these things out of foam swimming "noodles" that clip on with shock cord around the back of the boat. That way, you can set the back end down on the asphalt without scratching the gel coat.