Rallying with these kinds of players will give you the best practice IMO. If that's not available to you regularly then practicing with a ball machine set to a fast setting will definitely provide a lot of good practice. However, be aware that ball machines that do not have a topspin feature will need to be set at a low trajectory at the fastest settings to keep the ball in, this combined with the lack of topspin will lead to a very low flat ball that travels and bounces very differently from the usual fast/heavy topspin shots of real players. Its still good practice for handling fast shots, but you will likely have some timing/adjusting issues when going from the machine to real players. If you can, set the machine to so that it doesn't just fire to one spot.