How to thermal a RC glider with the good old down wind technique, Instead of flying upwind where you almost fly blindfolded in terms of thermals (Unless there is circling birds or other indications that there is lift) it is much better to have a wind indicator that shows the point where the wind is blowing to. Wait for a small Wind direction change or an increase in wind speed from the normal, and fly to that point or just a bit more upwind than this,, and when you find the thermal just start to circle and let it drift with the wind.
My gliders will rock the wings, lift the tail and accelerate when flying into a thermal, wait around 3 second and start the turn.
And a good rule when searching for for thermals: never make a down wind turn if you don't have lift, if you don't have lift at first, then you will fly back in the same bad air again :)
And on full house gliders also use the rudder in the thermal turn :)
Good luck
Soren