What instructions or guides do you recommend?

The project linked is a fork of the version on F-Driod. You can download the APK directly from the Github and use it just fine.

Any tips on how to actually learn this keyboard? Do I just force myself to use it as much as possible until the movements start to become muscle memory? How long might that take?

It will probably get made eventually, but they have said there is no ETA for now. In the meantime, you can upvote the suggestion on their feedback forums.