Ackoman

Hi Please forgive the newbie question! I've recently bought my 9 year old daughter a single line kite, and she loves it! I'm also loving it as it's bringing back many memories of flying kites when I was a young lad myself. My question is this. With a single line kite, it's easy to wind the string in and out whilst the kite is flying, but how do you do this for a dual line stunt kite? I had a stunt kite when I was younger, but I cannot remember how, or if, I wound the string in and out while it was in the air. Is it possible? Or does one just fly the kite at a constant length? Thanks Ackoman