Forums DIY Painting directly onto plaster Reply To: Painting directly onto plaster May 17, 2018 at 12:29 pm #305 pakpak 14 Posts Ive never heard of needing to sand fresh plaster, the finish should be such that it is free of imperfections….i served my time trowelling the stuff onto the wall. Priming the wall with a watered down emulsion will suffice but again not strictly necessary, a decorator told me not all emulsions are created equal, with trade paints formulated differently for just this purpose. Ive just re-skimmed my loft conversion, no priming, just deluxe trade paint straight onto the plaster.