Hi, we painted plastered walls a dulux silk but it didn't look very good. We sanded it down to 'roughen up' and painted over in Dulux Matt paint of the same colour. The paint has gone on well but in some lights it very patchy - it looks like areas of silk underneath can be seen through the Matt paint despite doing several coats of Matt. Want to get it repainted professionally but what is the answer to getting an unpatchy finish? Thanks in advance!