I believe a good painter can use a cheap gun or a nice gun. The cheap ones aren't machined as perfectly, settings may not hold as well, and parts may wear out quicker. But they work well enough for the quality of finish required for sign work. In most sign shops the level of quality does not usually equal body shop standards. If I had unlimited funds I would use the gun they used in the Matthews training schools that I have attended: Sata, with a digital readout ($800). You can really feel the difference in the way the gun handles. But the Harbor Freight guns work, too.
Keeping the guns clean is essential. One Matthews paint instructor told me that if you are not spending at least fifteen minutes cleaning the gun at the end of the day you are not doing a good enough job. Fifteen minutes, really? For many of you, that's enough time to completely break a gun down, clean and lube the parts, and reassemble it. So, is running a half pint of thinner through the gun really adequate as a cleaning routine at quitting time?
One of the advantages of Matthews Nuance (satin) finishes is that they don't show all your errors as much. At least, not like a high gloss autobody paint does. The paint is forgiving.
Matthews is a good paint system. It is fast drying and very durable. It is also very flexible. Matthews provides detailed instructions for painting practically any substrate found in a sign shop. Their training manual contains a wealth of information on surface prep and troubleshooting. Matthews color matching resources are unrivaled.
There is a comprehensive system of undercoats available, including a polyester primer made for HDU that dries quickly and sands beautifully.
Matthews is backed by the technical expertise and resources of the largest paint company in the world: PPG. Matthews seems to be dedicated to serving the sign industry. That could explain why they bought the One Shot, Chromatic, Spraylat, and GripFlex brands, among others.
If you use Matthews products you should be eligible for their two-day training schools. Even if you are an experienced painter the training is beneficial and you will learn. Matthews is not like most car paints. For example, it is designed to be applied in two successive medium-heavy coats, rather than the typical body shop practice of applying a light 'tack' coat followed by heavier color coats. Matthews is made for high production work.
Also, at the school, I learned the "15 Degree" rule for estimating dry times. It's in the manual somewhere if you don't attend the school.
Most Matthews products call for a 1.4mm fluid tip using an HVLP gun. But I have used tips as big as 2.0mm without repercussions that I know of. But that puts on a lot of paint in a short amount of time, and the paint booth better not be too cold. If the dried film thickness produced by that tip was too much for optimum durability, I never found out (Matthews durability is based on achieving the correct dried film thickness). But it looked good when I was done.
Paint booth temperature is important for Matthews paint to cure correctly. And you can't just paint something and move it immediately outside into the cold. Catalyzing will die and never recover. At that point, the paint is no better than hardware store paint and you've wasted money using Matthews.
I know I sound like a Matthews rep. Actually, if they were hiring, I would love to work for them.
Brad in Kansas City