Primer paints may be oil- or water-based and are used to seal unpainted surfaces to prevent covering coats of paint soaking in. The appropriate type of primer should be used for the surface being painted - wood, metal, plaster or tiles. There are some 'all purpose primers' available which are designed for two or more of these surfaces.
A good interior paint job is often 50% preparation and 50% painting. Do not rush in preparing the surfaces in your eagerness to get at the brush or roller. If you do not prepare the surfaces properly, you'll be back with the paint brush or roller in a few months.
Take off the chrome molding around both the windshield and rear window. You can pick up a special tool at your local Mustang shop or by mail order that removes these quickly without scratching paint. Of course your paint is probably not in great shape at the moment, so a large flat screw driver will also do the trick. For some classic cars it makes sense to even remove the windshield, but classic Mustangs have chrome molding that will help cover any slight overspray.
When all of the spraying is complete, its time to remove all masking tape and paper and start touching up your entire home. This step is pretty time consuming because this is the final stage that really makes your home look good. The more time you spend here, the better your home will look.
The first step is to cover the surface with a coat of paint, using your regular paint brush, or spray, or roller. Then, while the surface is still wet, take the dry stipple brush and energetically with short strokes drive the ends or the bristles into the wet paint. Be sure not to brush across. The result will be clusters of dots. Every few minutes wipe the brush with a cloth, to keep the bristle ends clean and dry.
Knock down texture is basically a orange peel that is sprayed on and allowed to "set-up" for a minute or two then gently "knocked down" by running a 6" drywall knife over it, "knocking down" the surface of the texture. Although knock down is a flattened version of orange peel, I suggest you do not use a spray can of orange peel, the knock down comes in its own spray can and the results are much better, again experiment before spraying it on the wall. However, If ever you apply any of the textures to the wall and are not satisfied with the results, wash the texture off immediately before it dries, then allow the wall to dry and try it again. Once you have the texture applied to your liking and you have allowed it to dry, you may want to paint the patches a couple of time before painting the entire wall, especially for walls where the paint to be applied will have some sheen. Multiple coats on these areas will make them blend in, unnoticeable, with the rest of the wall. You will know if the patches need more coats of paint, because the patch/texture will have absorbed the paint causing the spot to look duller than the rest of the existing wall.
To balance, you must grasp the interconnectedness of color schemes. All these interactions are defined in the color wheel, and it has been used to build color schemes for centuries.