Krita is the best painting tool I know, some years ago, before I know Krita, I used Project Dogwaffle. Its an not very expensive ($29) digital painting/animation app, but they offer also the old versión as freeware (very old app, as you can see in the page somewhat vintage, but works fine) which I used. Very good app, but Krita is somewhat better, actual and FOSS.

For those who want to compare

Official page for the current Dogwaffle (Howler 2023)- This version has results somewhat more realistic results than Krita, but not much.

https://www.pdhowler.com/WhatsNew.htm

Screenshot Dogwaffle free