Plastic sheathing and masking tape was not available at the end of the painting project for whatever reason, I have no idea, but you have a Paint Brush that if not cared for will eventually dry up. Last solution that works well, is to take a sopping wet rag, wrapping the Paint Brush up like that burrito you missed wrapping up earlier. This will buy you some time until either you use the paint brush again, or you can properly clean it.
If you decide to do your own body work discuss it with the paint shop first. They'll probably have recommendations on the type of primer you use. Some brands will be more compatible with their primers or color coats. The rule of thumb is to stay within the same brand of paint, both for prep and color. Even the cheapest paint shops typically use a brand name on their intermediate and higher paint jobs. Find out what it is and use the same brand as your primer coat. This will ensure you don't create adhesion problems for yourself down the road.
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.
Try before you buy Colour cards are fine for making an initial selection but you will want to see a true paint sample in situ before committing. Tester pots vary in price from £1 to £4. Paint onto a sheet of paper that you can move around the room to enable you to see the colour in different light conditions. The effect varies greatly. The window wall can seem dark while the wall opposite will be flooded with light. And of course there is a dramatic difference between natural and artificial light. Finally paint a patch directly onto the wall to gauge the colour, coverage and the final finish.
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.
The principal ingredient in whitewash is lime paste. A satisfactory paste can be made with hydrated lime, but better results are obtained by using quicklime paste that has been slaked with enough water to make it moderately stiff. The lime paste should be kept in a loosely covered container for at least several days. Eight gallons of stiff lime paste can be made by slaking 25 lbs. of quicklime in 10 gallons of water, or by soaking 50 lbs. of hydrated lime in 6 gallons of water. After soaking, the paste should be strained through a fine screen to remove lumps or foreign matter.