I used that groover on my 36s:
It'll take a while, but it's not terribly hard. Basically, if you're only grooving one or two sets a year, that groover is fine. If you'll do much more than that, get a really good (read: insanely expensive) one.
Just get the tire out in the sun on a warm day, and make sure you have the balde in the right way: only one side is sharp.
