Fire-retardant paints do not resist fires completely but its fire-resistance formulation prevents it from fire in spreading fast.
Basically what you're looking for is a good, solid foundation of existing paint that is stable and still strongly bonded to the car. Many times an original factory paint job, even after decades will meet these criteria.
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.
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.
It's funny, but many of the colors that a paint company puts in its line would never look good painted on any wall. The colors are 100% used to grab your attention when you are perusing paint displays. People are helplessly attracted to bright colors; they are much more eye-catching and far more interesting to our brains.
So how does a paint company accomplish this color hypnosis of potential customers? Well, it starts with the sample card. Have you ever noticed how the brightest, most saturated color sample cards are always the first row you see in a paint display? Well you guessed it... paint companies are playing with a loaded deck (of sample cards, that is)!
Another popular color wheel called the Munsell color wheel, is slightly more involved. Instead of 6 basic colors, the Munsell wheel consists of ten colors: red, yellow-red, yellow, yellow-green, green, blue-green, blue, blue-violet, red-violet and violet.