Cleaning brick wall of old solid plaster. (Internal wall)

Hi guys, Ive got an old 1930's californian double brick place that is falling apart. Latest thing is the bathroom have decided to bite the bullet and atempt a reno myself. So was hoping to just chip away the loose plaster around a few cracked areas (Solid plaster) then patch up. Unfortunately for me the whole wall was drummy as and the plaster just fell off the walls! So the floor was rotten also so gutted the room completely. I have made a new floor frame and fixed in. But now I want to re render the walls. Decided to use solid plaster again instead of gyprock. But i dont think I can really use lots of water and a brush to clean down the dustiness and old bits of render still on the brickwork. Does anyone know the best way to clean down the brick work of an internal wall without saturating the new floor frame in the process? Can I use a damp sponge and rough brush? Probably should have done this first right?

Any help is appreciated. Thanks Chris.