I bought similar tool to what is used in this video. I don't want to share link, because I don't want this post to be treated as advertisement. I even made similar one from scrap, you can also go that way if you want. The tool on Ali costs 10-20$ so I think anyone can afford it. I've been doing some repeated top spin exercises (as shown in Ti Longs video) and it helped me improve my game big time. After 3 weeks of training with this tool I managed to break my current skill ceiling and defeated a person who I struggled with for a long time.
It's not a silver bullet. The major issue I have, is lack of everyday training to really burn in the muscle memory. This allowed me to get that everyday. I really encourage people who want to improve to get at least one of these to work on their technique.
A couple of things that require a lot of attention when using this (after a long discussion with my coach):
- always return to ready position
- shorten my stroke
- record myself and make sure everything is clean
- make sure the ball is screaming with spin (the brass bearings make a certain noise when they reach high spin)
- make sure that I transmit both forward momentum (please correct this wording dear physics forum experts) AND spin. Otherwise my contact will be trained to be too thin.