When I'm doing mockup prototyping for user interfaces, I still prefer painting by hand rather than using mockup tools.
I feel confident with draw.io, but not for the first prototyping session.
There you just have to be creative. And creativity does not come from a UI design tool.
Since I just got a new Onyx Note Boox Air, I've created new templates for mobile device mockups.
There are three version inside the package, two iPhone and an Android mockup.
Just download them and put them onto your device in the
The templates are available from my GitHub repository:
Download the templates
There is also a GIMP source file here.