I have a couple of soroban at home. One has lovely, bright, colourful beads to attract the children. They are attracted, they try to use them as roller-skates. Which soroban drilling app have you used?
https://play.google.com/store/apps/details?id=br.net.btco.so...
There are Youtube videos explaining the algorithms. A basic exercise is just counting, and then do a countdown. And then try to do it as quickly as possible. Then do it in intervals of 2 rather than 1, then 3, and so on.