if you're fighting with them in the TA, it's usually ok to shoot as well, unless they ask you not to
as for turning, you don't always need to be at a certain speed, simply because it's impossible. just pull on the stick! you'll slow down, but as your turn rate decreases, your turn radius decreases, which is actually more useful in an all out turnfight.
don't think about it too much, just turn. put flaps out when you feel you need to (flaps don't do much to the turn rate, but greatly reduce turning circle, which is a good thing. they do slow you down and lose energy though, so keep tabs on them) one or two notches of flaps can be put down in the F6F pretty much ASAP, as they really help stability and turn rate as you come into the turn with speed. once you get slower, you can add more flaps to turn tighter.
what you need to learn is when to use them, and get practise with them
also, you must make sure your stall limiter is OFF. it's harder to fly with it off yes, but you will be able to fly your plane on the edge of the stall.