I've now updated ChickenPaint 2 to make it usable on smartphones (especially ones that have a pen available for input).
Floating toolbars can now be collapsed by clicking on their headers to get them out of the way, and the tool palette is automatically dismissed after you pick a tool. There's a new grabbing-hand tool in the toolset for panning the canvas (instead of using the scrollbars).
It'll look like this when you first open a drawing:
If it isn't styled like this for you, make sure you have picked ChickenPaint 2 on your Oekaki painting settings page.