Freshly painted walls often look blotchy. The color is uniform, but the sheen isn’t consistent. This usually occurs over the holes and cracks you patched with a filler or drywall compound. The porous fillers absorb the paint, dulling the surface (a problem called “flashing”). When light hits these dull spots, they stick out like a sore thumb. The smooth patch also stands out in contrast to the slightly bumpy texture of the rest of the wall. A quick coat of primer is all it takes to eliminate ﬂashing and texture differences.
Excellent advice because there are many unskilled workers who are "trying to pull the wool over the customers eyes". One has to study about the project for which they are in need. I happen to need dry wall repair and painting done in my home and feel the advice in this article will be a great help to me in hiring someone who is ethical and does good work. Thanks.