My daughter (13m) also 吾肯換尿片 recently and putting force on her will make her outrage.
I've to play with her in order to get the job done.
If he doesn't drink water than give him some juices.
Change to new tooth brush (cartoon) or falvour paste (taste/smell good) that he likes to encourage him to use it. Let him have his choice....
Tell him that he has to take de-worming in order to kill all the parasitic worms/bacteria/germ in his stomach if he doesn't wash his hand before taking any food. Explain to him that he'll suffer from bloated stomaches, pain & diarrhoea.