I'm not sure how other people do it, but we used a cable attached to our trailer to launch our Cal 25 (4' draft also). We just popped the trailer off, let it all slide into the water and pulled the trailer back out with the cable.
I've heard about people doing that. Do you detach the trailer on flat land, hook up cable (take out the slack) and then push the trailer down the ramp by hand? Using the tow vehicle to slow the descent? What happens if the trailer wheels go off the end of the ramp before the boat floats? Does that mean I'll need to back the trailer into the mud, and try to pull boat and trailer up onto the ramp when hauling out?