A couple of added thoughts:
The Polly-S paint prep does work well. It also helps to sand the body with 800 or 600 grit wet/dry sand paper and apply a thin coat of primer or undercoat if shooting candy or pearl paints. Static electricity will attract hair, dust, and/or small particles. While spraying the paint in the dry air it stirs up some static electricity. A humidifier helps reduce the static electricity problem. A rattle can should be well shaken before and during use to minimize the small clobs of pigment that make an ugly appearance in the paint, especially candy colors.
If using an airbrush the paint should be filtered before thinning and after thinning. The airbrush should be cleaned before each use. Use a tack cloth and tack off the model lightly with the tack cloth just befor spraying. As mentioned above wetting down the surrounding area is a good idea for keeping down dust. Remember you are stirring up the air when you spray so wetting the area keeps down the dust, hairs, etc.
Warming the paint expands it and as it cools it help it to lay down, i.e. less orange peel. This is especially true for enamel like Testors MM. To avoid runs apply paint in coats and let each coat get "tacky" before applying another coat. The first coat should be a thin coat and it should be very tacky before the next coat. It is referred to as a "tack" coat and is specifically intended to minimize runs. This is again especially true of enamel. If you are spraying in approximately 70 to 75 degrees F use a thinner with a similar "flash point", that is the temperature at which the thinner readily evaporates. Most model enamel reducers or thinners have this as a flash point (approximately room temperature). A higher flash point thinner can slow the drying time and can give the paint more time to lay down, again minimizing orange peel. However, the various brands of model paints do not offer thinners (reducers) with variations in flash points.
Those who use real automotive paints can get thinners with different flash points. However, using the newer chemical paints can be very hazardous to your health and they are not recommended. Some of these paints are so toxic that rubber gloves are required to be worn when sanding the dried paint or primer because the chemicals can be absorbed through skin contact.To say one of these paint jobs is "to die for" may be truer than you may think! If you have not had the training on the use of these paints, and access to the necessary safety equipment, DO NOT USE THEM.
Take a walk through the cosmetics department of a store and look at all the neat colors that are used for nail polish. It can be thinned and sprayed. The brand name has its own thinner (remover). However, this enemel will eat the plastic so a barrier is necessary if you use it. You can protect the plastic with an automotive lacquer primer applied in thin coats so it does not attack the plastic. You can spray some out of a rattle can into a bottle and then spray it through your airbrush.
Lastly, protect your lungs and wear a mask.
A few thoughts from 50 years of experience painting models and more than a few real cars.
It is important to not mix brands, that is, use Testors thinner with Testors paints etc.