Having never seen one before, I bought a (MasterForce) "Rub Brick"
(6"x3"x1", $9.99 at Menards) thinking it may help to clean up my concrete
garage floor which is to be my workshop floor. I "applied it to about 6
square feet in an inconspicuous area using also a bucket of water and a
towel. It provides decent exercise. I may try using it to smooth some
Quikrete repairs someone else did in the past--actually, I tried it in one
spot and the result looked pretty good (not sure if I weakened the repair,
but I'll be mixing some Quikrete, sand and vinyl, in the spring anyway.).

I am thinking now that I may work around the edges (and the water softener,
etc) with the plan of bringing in an electric concrete grinder in the spring
to do the rest of the floor.

I think the rub brick may be giving me a good idea of what I might expect
from the concrete grinder (true?). Don't they use the same sort of stone
(although I know "diamond" is available for the powered units)???

I noticed in the last few minutes, online, that the tool is often used to
help prepare concrete for tiling. Is there anything inappropriate with the
way I am using it? P.S. I wore a dust mask, but, once I started using
water to help get the dust out of the brick, I don't think there was much
need. Should I be concerned about how flat the cutting stone stays (I'm
mostly only taking off paint, grime, etc.--that is, I'm not cutting deep)?
I am probably doing things the hard way, no?

Thanks!
Bill