I've successfully wet sanded varnish with 400 grit paper and it worked fine. A maroon Scotchbrite pad is supposed to be 400 grit so I can't see why it wouldn't work.

Laszlo

I concur with Laszlo, I've done it & yes it works fine.

As you're doing varnish, not cured epoxy, go easy on the pressure you apply & check your results after wiping work surface then letting it dry. Wetting does knock down the dust otherwise produced while creating another kind of 'mess' that has to be dealt with.

   I went ahead and tried it, worked ok but didn't cut as aggresively or as deep. Of course no dust but that's offset by having to use more pressure and takes longer to get that gray haze. I'll go back to the dry Scotchbrite today. Also easier to see the progress. And yes the "mess" is another negative.

SB