please help am rendering bottom half of my house have i,ve been told to use washed sharp sand soak walls first do 2 coats 1st 4to1 2nd 5to1 and use 3in 1 additive comprising of waterproofer plasticiser and retarder was told this will slow down the render from going off to quick also somebody told me to put pva in 2nd coat as it makes top coat stronger is this correct and if so is pva neat or watered down please help as am being told so many different things many thanks