You scuff up existing paint for two reasons. First, you want to get rid of any oil, grease or dirt trapped in the top layer of paint. This is the stuff that cleaners and degreasers can't get off. The second reason to scuff is to set up a physical bond for the new primer and paint to adhere to. You want to give the old paint some tooth so the new sticks better.
Cold water paints of the casein type may be applied either directly to a plastered surface, or the surface may be first given a coat of primer-sealer to equalize uneven suction effects. The same is true of resin-emulsion paints, with the recommendations of the manufacturer of the product being given preference in case of doubt. Since resin-emulsion paints usually contain some oil in the binder, they should ordinarily be applied only to plaster which has dried thoroughly.
Step three: go online and study the basics of shadow and light. It's a visual thing, and too complicated to talk about here. But once you see it, it'll come to you quickly. Simply Google "shadow and light in painting" and the basics will come up. Once you know these rules, you can apply it to any shape, any form, any painting. And it'll make you keenly aware of shadow and light on virtually any object on earth. It's what makes a painting three- dimensional and expensive looking. You can also buy art books on shadow and light at any bookstore. But make sure you sit down for a couple of hours and study it. It will come quickly to you, I promise.
Are the contours rough or concealed?
Color can make a big difference in your life. I know from experience. Before I learned my right colors, I had a closet full of right and wrong colors. Of course, the colors did not work together and definitely did not coordinate. I had no idea of the difference that coordinated colors can make. Further, I had a drawer full of lipsticks some with gold undertones and some with blue undertones.
When you plan with split complementary colors, you begin with a single reference color. Next, choose a color from either edge of the complementary color and use it. While the complementary color scheme is a little more obvious, this scheme can fail totally if you just use paler versions of your warm colors. By the same token, picking a a warm undertone for the main contrasting color and combining it with two cool tones will showcase the warm tone.
Satinwood or semi-gloss - These paints are commonly used on woodwork, such as skirting boards. This sheen level is between eggshell and gloss.