If you are grappling with the problem of choosing a woodwork colour to go with neutral walls, check out Architectural Colours by David Oliver, the founder of Paint & Paper Library. He arranged his off-whites for ceilings, cornices, walls and woodwork in chromatical groups and the concept has been so well received that chromatically arranged colours, such as soft greys, greens and pinks, have been introduced.
Store your leftover paint in plastic Rubbermaid beverage jugs or other plastic seal-able containers. Paint left in the can always gets funny after time. Either the can isn't properly sealed of it gets exposed to extreme heat or cold. I like to store my paint inside where the temperature is controlled.
Also, when checking the paint, be realistic and don't ignore areas just for the sake of convenience. It will cost you more in time and money later. Typically if one area of the paint is cracked or peeling, then the paint on the entire car is suspect. Maybe the rest of the car just hasn't quite reached that point of decay, but it will shortly. So if you only fix areas that look bad, you'll likely find that you wasted a paint job when the other areas start to crack or peel in a year or two.
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.
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.
Analyze your existing paint. The first step before determining if a budget paint job will work on your Mustang is to assess the current condition of the paint. In many cases you can prep and paint directly over an existing paint job, but only if it's in solid shape.
However, if you put a coat of pure white primer (which has a score of 0) on top of the brown color wall first, this immediately brings your luminosity score down to 4 (8 + 0 = 8/2 = 4, the average). This means you may only need one coat of yellow paint to give you the right hue and saturation. In reality of course, you will always want to do at least 2 coats. But even with a total of 3 coats (primer and paint) you are way ahead of the paint-only option.