Is it true that if you use a squash racket to clear birdies, will that actually train your forearm? Anything else to train your wrist or arm strength and endurance?
You bet it will. ;-) Personally, I also find it very efficient in fast and flat backhand/forehand drives from midcourt to midcourt.
Mag is right... do it all the time. I've bought a squash racquet specifically for that purpose. I also wrist curl a 120 lbs bar which really helps.
I use an old racket cover (the one that only covers the racket face) for shadow practice at home! After about 30-40 strokes, I can really feel the stress on my forearm.
I do similar thing. I have attached some strips of metal to the top of an old racket and practice shot execution with it. The extra LB or so of weight at that point on the racket makes a lot of difference when you shadow the same shot repeatedly. Mark