Thanks for the info! I already gave him a bath in it this evening
but I wasn't sure it'd be good for him so I used about a half/third of what the package recommended.
Also, he has almost full control of right leg (still too weak to walk, but great progress), and was gently pushing himself around the bath.
Left leg also has movement but isn't quite as strong yet as his other one though. Also, my mum was worried this morning that his leg movement was just muscle spasms, but they seemed to be working fine this evening and also responded to touch/massaging and he was able to push off my hand a bit.