To balance color, you must grasp the interconnectedness of color schemes. All color interactions are defined in the color wheel, and it has been used to build color schemes for centuries. 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. Once the drywall compound/spackle has had sufficient time to dry, you will need to lightly sand the surface of the repair to smooth out any ridges that may have been caused while "coating" the patch. Once you have the surface sanded smooth, take a wet sponge or cloth and, by lightly washing/rubbing, blend the outside edge of the drywall compound/spackle back into the wall. For a smaller repair, you can wash away the excess drywall compound, leaving only the compound/spackle only in the area where the indent was filled. For a larger hole, after filling, sanding and using a wet sponge to blend the outside edge of the compound back into the wall, it may be necessary to texture the area in order to give the smooth patch the appearance of the existing wall.
Alkyd is an old interior paint made newly popular by a change in solvent - a super-refined petroleum chemical that has almost no odor. It is not a water paint. You thin it and clean brushes with mineral spirits or turpentine, or, if you want to retain the odorless feature, with the new odorless solvent. (Ask the paint-store man for just that, odorless solvent). Always use a sanding block for flat surfaces. Just your hand behind a thin piece of sand paper can leave grooves and low spots. It's also easier on your hands. For inside curves try wrapping the sand paper around a short section of garden or heater hose. This will help approximate the concave curve and help stay away from sanding through hard edges. On hard edges, like the top ridge of a fender or leading edge of a hood, you need to do this by hand. A sanding block will quickly dig right through the paint on a hard edge and take you down to bare metal. This means primer and more sanding. For stippling you need a special brush; get one that is flat, and has short, stiff bristles. The reality is that the guys shooting paint, even at the cheapest shops, know how to do it. They spray a dozen cars a week and have plenty of practice laying down smooth, consistent coats of paint. They work quickly and efficiently because they have to or they don't make money. They don't really make their money on shooting paint. They profit from body work because it takes time and insurance work because it pays well.