All of my 3-whistle work is in a camp setting...so far. I will say that the hardest part for me was being slow to rotate when at L (I also had a little trouble picking up the rotation when at T but soon got pass that).
The one piece of advice at my first camp this year on being slow to rotate was "If the ball goes to the other side of the floor, close down quickly and count 1 second. If it hasn't come back to you side...MOVE." Using that as a guide helped a lot. Remember, just because it works for me doesn't make it the best approach.
Another thing said to us at camp repeatedly..."Even though a lot of people here know you missed a rotation...at a game there are usually only 3 that know it was missed...maybe not even 3"
Call the game and ask a lot of questions. That is what I did. If I can get the hang of it anyone can.