Re: casting a 5wt?
All above advice is right on, but I'll add a trick/short-cut that may help. Try casting with your index finger paralell to the rod, instead of curled around it and part of the gripping force. You won't be able to cast the rod as force-fully, and this will likely help you figure out what is the optimal amount of power with which to cast that rod. Once you've got that down, feel free to go back to casting with the normal grip.