Im getting the hall stairs and landing ready for painting, so yesterday i filled in any dents cracks etc on the wall, let the filler dry overnight and this morning sanded down the filler until it was totally blended into the surrounding area and painted over the filler with the original paint now the filler and area around it is dull looking, so before I start painting the walls is there anything I can do so the filler isn't visible when I put two or three coats of matt paint on the walls. TIA