I wasn't sure whether to reply to this one, but here goes. Those of you that use a spray or just flick your water on using a brush are completly missing one of the main purpose's of using a brush when troweling up. Under many circumstances the troweling up will go better by laying the wet brush on the wall/ceiling in front of the trowel. This breaks the surface of the plaster and makes troweling up easier, using a spray just can't replicate this. When I finish a hit of setting my spot board is clean ready for the next one, no fat all round the sides, use a brush wipe the trowel straight of into an empty bag. Don't make more work for yourself having to clean all that crap of the board, it all costs time.