One precaution: You can't paint with it in cold weather. The chemical reaction that transforms the water solution into a durable finish will not take place if the temperature is below 50°. (Conventional oil paints don't stick well in cold weather, either.) You'll need a large compressor, not just the typical 20 gallon variety most of us have. This is a 60 gallon, vertical compressor with typically a 5+ hp motor. Then you'll need a decent paint gun (possibly 2; one for primer and one for color) which again is an expense. Then there's the question of where you'll paint the car. Renting a paint booth is best, but can be expensive and hard to find. You can always seal up your garage or shoot out in the wetted down driveway, but you'll inevitably get dirt and moisture into the paint. Remove side view mirrors (unless they're to be body color) as well as exterior door handles and locks. This will take some extra time because you need to remove the interior door panels to get these off, but it's worth it. Head lights, tail lights, marker lights and license plates should come off too, but you'll need them in place to drive to the paint shop. So bring some tools so you can quickly take these off once you arrive. Depending on the year Mustang you can just take off the chrome bezels or rings. The shop can then easily mask the headlight or tail light itself and still get plenty of paint around the edges.
Set up costs are normally included with any home improvement job, painting separate times for complete exterior painting can essentially cost double, unless agreed before work begins in painting quote. If paints have been allowed to stand and hard lumps or skin have formed, the skin or scum should be removed, after which the paint can be stirred and strained through screen wire or through one or two thicknesses of cheesecloth. Airless Tip: If you have somebody who can start masking off the trim, have them start on that while you convert the airless to a new color. When changing colors with an airless paint sprayer it is a good idea to have a second bucket filled half way with clean water. Place the intake hose in the clean water gently without getting the old color everywhere in the water. Take the tip out of the airless and spray all of the old paint out of the hose and back into its original paint bucket. Be careful when doing this that you recognize when the paint starts turning watery. When it does point the gun into the first bucket and spray until it looks pretty clean. It doesn't need to be perfectly clean. When it looks good, clean off the intake line in the clean bucket and get the old color off the intake line. Now place the intake line inside of your new trim paint. "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.