Yeah sounds like you were on the right track already, no problem. Yes for sure it’s better to have an effective shot that what looks good, however what I would say is that if you were getting it to spin bac on the table then it means you are getting good spin and a nice contact on the ball so if you can reproduce this feeling but get the ball to just bounce twice and then spin back after the second bounce, that is perfect! Not easy of course but something to aim for anyway.
So as for training the flick and touch combination I would do it as you have described but also combine them together so your lad can serve maybe short into your backhand with spin variation and you have to choose whether to touch or flick, this will improve the fast decision making that always has to happen in a match. Also a great drill for both short touch and flick together which I use is your lad serves short backspin to you, you touch back short, he touches short again and then you come in with the flick, this reproduces the scenario of both players trying to keep it tight and finding the chance to flick.
You can also do it as a game situation where you both keep touching short until either of you feels the ball is there to be flicked, again great for decision making and practicing the shot in a real scenario which I feel is very important 🙂
