[firefly123]

got to do a wall clean with wfp anyone use a pry-spray on brush before cleaning walls

[mark dew]

I cleaned the painted exterior of a big old house 3 years ago. It was a pink background covered with green algae.
My customer supplied a 5 ltr tin of a product called or made by sandtex. I think he said it cost £25??
Dilute and brush on 1 day. Go back the next day to brush off.

[EandM]

Just use bleach, cheap Tesco stuff will do.
Dilute with water about 25% ( depends on how grubby the wall is ) and apply to wall with a long pile paint roller on a pole.
Give it a couple of coats and leave over night then rinse off with tap water.

I've been painting walls for 25 years and haven't yet found anything as effective / quick.