Back in the days when I glided in the UK (eighties), we called in on the glider air frequency when we were entering a Cu. And we had to wear a parachute in case of a midair. No training needed, just keep the T&S on rate 1 and monitor airspeed. Most gliders have speed limiting airbrakes if you start getting out of control. In my limited cloud experience the lift often smoothed off inside the cloud. As the best days for this were when there was scattered Cu, say 2/8 or 3/8. there should be no reason for a VFR power pilot to penetrate or be near the cloud and we would never cloud fly in the IFR corridors or controlled airspace.