I have a small 2 inch dia castor wheel mounted on the front of my trailer, this helps rolling the trailer around on cement and blacktop, but is useless on gravel and grass.
My trailer only weighs 150 lbs, what I do if I want to launch at the beach I shift my boat back on the trailer a foot or two so the balance point is on the rear trailer wheels, then strap the boat with one strap to secure it. I then pick the front of the trailer up and walk it to the beach (with the receiver in my hand). The big 12 inch tires roll nicely on fairly soft sand and over terrain. Sometimes I have the AMA's out, the tramps on, and the sail's already up (setup in the parking lot) before walking to the shore.
The only awkward part is getting the boat back on the trailer, since there is no car to hold the trailer still it tends to want to push away as you load the boat. What I do is lift the boat onto the back of the trail, hook up the winch, then winch the boat onto the trailer. Once the boat is on the trailer I walk the trailer back to the car and hook up the trailer to the hitch, slide the boat back forward a couple feet to it's normal position (so there is weight on the hitch). I then fold the AMA's in and put the rest of the gear away, basically everything just lays on top of the hull for transport, I never remove anything off the boat, all 3 sails, the anchor system, mirage drives,and both the motors just stay with the boat always.
When I get home I rinse the boat off and roll it into the garage (on the small castor wheel, on the concrete driveway) ready for next time (takes all of 5 minutes)
It actually works pretty well for me.
You can see the small castor wheel in this pic.