How helpful will .22 practice be for getting better with a .40?
A lot. It's all about quality trigger time.

Or you can use snapcaps, and practice your grip, trigger, sight picture while dry shooting your TV, the cat, wall sockets, etc...
I am always dry shooting, my wife calls it "playing with my gun again"
I keep reminding her "This is my weapon, and this is my gun, one is for killing, one is for fun!
Her standard reply is : Ya, well don't confuse the two!"
