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.
Hope this helps you in deciding complete exterior paint job, or partial trim only exterior paint job, saving painting costs when you can, from your local area painting contractor.
Water-thinned interior paints are calcimine, casein, resin-emulsion, and gloss water paints. Calcimine consists of powdered whiting and clay mixed with an animal-glue binder and a preservative. It cannot be recoated, but can be easily washed off before redecorating.
If paints have been allowed to stand and hard lumps or skin have formed, the skin or scum should be removed, after which the paint can be stirred and strained through screen wire or through one or two thicknesses of cheesecloth.
If red is the color of fire and yellow is the color of sun, then orange color, which originates from the blend of these two colors, combines both warmth and light in it. Light muted orange accent will give your interior cosiness and warmth, especially in the room with windows facing north. Bright orange color in the interior on the other hand is more of a claim for originality.
Another popular color wheel called the Munsell color wheel, is slightly more involved. Instead of 6 basic colors, the Munsell wheel consists of ten colors: red, yellow-red, yellow, yellow-green, green, blue-green, blue, blue-violet, red-violet and violet.
Painting ceiling does not require premium paint. You can use flat $15 to $20 ceiling paint. I use Sherwin Williams PRO-MAR 200. Painting ceiling requires a lot of physical work and plenty of drop cloths. If you are not up for the challenge or have very high ceilings contacted a professional will prove to be a smart move.