Dulux Diamond Matt on top of supermatt

Before we are talking about products of paints. As I am reading, it seams that you wanted to paint hallway walls in light colure finish over a dark finish. What is important before painting to know, that there is no any condensation on walls or even a dry air. Sometimes dry air can cause premature drying of paint during painting with roller, and can lead to a peeling of paint that can lead you to a slow and not so good finish. As you mentioned that walls were painted in dark finish, it is advised to paint first coat (or even two) in white ordinary emulsion paint. It is good to know first of all, that brilliant white can neutralise over very dark colure and it can be called as form of primer coat. Final application of (in your case) Dimond Dulux Matt can be very economical because it does not need more then two coats of paint for finish. Diamont Dulux Matt is coming as very tick paint that can lead to premature quick drying. It is advisable for paint to be diluted with water, for a smoother painting. And the last thing: if you filling up and sanding walls, because of dust, before painting all walls should be wiped out with wet sponge. Leaving walls clear of dust, for smoother painting.