I'm not sure if the flat forehand drill is the same as the one I have used in the past ... but I can tell you that I do use a "kind of" flat forehand drill off a wall and it is really, really hard to hit an absolute flat forehand routinely! I inevitably put topspin even when trying not to ... I don't think I've ever hit 5 in a row where I could read the label after impact ...
Q: on the ball machine thing, where do you place it on the court? Also, I'm worried that I'll clock the thing and knock it over...
FYI: My Prince model 3 is almost ten years old and truly "man's best friend" ...