I have been asked to clean the render on a 1930's bow fronted semi but have never done this sort of clean. I am thinking of spraying on Hypo, scrubbing with an old brush on my pole and then swilling down with water. Would that do the job or have I missed something? As this is my first job I have a couple of questions 1. What strength Hypo would you use? I think mine is 15% 2. How long do you leave the Hypo on for? 3. Would you clean with UBIK first? 4. What is the going rate for this sort of job? 5. How safe is the Hypo at the sort of strength I would be using? Any help would be much appreciated.