Cheaper then doing it yourself. Some would argue that if you're going to all the trouble to fully prep the car yourself, then why not just shoot the paint as well? Why get a shop involved? The answer is simply that you'll get a better job and for less money. Some would argue with this, but the fact is that if you've never sprayed a car before then your first car will have a steep, and expensive learning curve. Laying down an even, consistent coat of paint takes considerable practice. Also, paint and equipment is not cheap. You'll need to buy primer, color coat, clear coat, reducers & catalysts. None of these are inexpensive and you can easily spend as much in paint materials alone as the cheapest paint job at Maaco or similar shop.
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.
There is still no standard labelling scheme for paint. The blue globe label, pioneered by B&Q, led to VOC reduction on the mass market and has been adopted by other brands, while the European Ecolabel, recognised in 15 EU member states, looks like a flower and appears on brands such as Earthborn. Germany also has a Blue Angel label and there is a green Nordic Swan as well. You will find more detailed information on most of the paint company's websites, as well as a wealth of practical and design advice.
"Boxing" is a good method of mixing paints. Since paint is a mixture of solids and liquids, it is important that it be mixed thoroughly before using. To do this, the greater portion of the liquid contents of the can should be poured in a clean bucket somewhat larger than the paint can. Then, with a stiff paddle, the settled pigment in the original container should be loosened and any lumps broken up. After this, mix the material in the container thoroughly, using a figure 8 motion, and follow with a lifting and beating motion. Continue stirring the mixture vigorously while slowly adding the liquid that was previously poured off the top. Complete the mixing by pouring the paint back and forth from one container to the other several times until the entire amount is of uniform consistency.
Have plenty of newspaper around. After you clean your brushes wrap them in a plastic bag.
Malabar and Designers Guild offer some striking brights while the new Shades of Sanderson comprises 120 colours tailored to Sanderson's collections. If you are aiming for a more subtle backdrop that will flow through several rooms, it's wise to stick to neutral shades. Kevin McCloud's Elements of Colour for Fired Earth works especially well with our cool, northern light.
You're not looking for perfection here, but you do want to eliminate every shiny spot of paint. When properly scuffed the paint should have a smooth, but dull matte finish.