I don't think there's much you can do as far as drills go. I would do something like this:
Sink 50 3 footers, 40 6 footers, then 30 9 footers. On another day do the same but with 4 and 7 footers. Another day hit sink 50 putts from random distances. Add some video every now and then to check your set up and stroke.
Repetitive 3 footers sounds mindless, but I think it will help you to ingrain your stroke and give you confidence on the course.
Also, looking at the product, I really like that it doesn't have a ramp. Most putting mats do, and that turns me off because I think it encourages you to run the ball too far past the hole.