Dunking (keyboard only)

Does the keyboard limit dunks as much as I think it does? I've tried many times, and I can't even modify the most basic dunks. Any help with modifiers using only the keyboard, and dunk tips in general, would be greatly appreciated.

U should get a joypad with an analog stick
And, YES, there is a small limit of dunks u can do on a keyboard(no modifiers at all on the keyboard)