The dual-action sander (commonly known as a "DA") you'll need is an air-powered orbital sander. The most common is the 6-inch model, though many production shops use a larger, 8-inch model. The size designation actually refers to the diameter of the sanding pad and the sandpaper discs used with it. It's called a dual-action sander because the pad rotates two ways: while it's spinning on a central shaft (much like a wheel spinning on an axle), it's also moving in an orbital fashion. The combination of these two actions results in a much smoother surface with no galling, as you'll find with a single, circular motion like that of a body grinder.
Speaking of grinders, there are plenty of situations that require their use. From grinding welds to grinding out fields of old body .filler, the single, circular motion of a grinder fitted with a coarse-grit disc makes quick work of chores like these. Grinders come in both electric and pneumatic versions, but you'll find that a 5-inch, pneumatic model tends to be the lightest, smallest, and most versatile (but they do use a lot of air to operate).
There are a couple more air sanders that'll save you lots of time and elbow grease hen doing bodywork. One is called a "jitterbug" and the other a long board," and the main function of these sanders is cutting body filler on large, flat surfaces. The jitterbug is an orbital-type palm sander that is available for use with sandpaper in either of two sizes: 32/3x9 or 4x8 inches. The long board is a straight-line sander-in other words, its pad moves back and forth in a straight line. Long-board sanders use "long skinnies," which is slang for sandpaper that's 2 3/4x17 1/2inches.
Hammers, dollies, and body files are a must for any type of metal-shaping or dent repair. There are many specialized types of both hammers and dollies, but most chores can be accomplished with just a couple of multi-use designs. As far as body hammers go, a general-purpose dinging hammer (a double-faced, flat-head design) and a general-purpose pick hammer (a single face on one end and a pointed shaft on the other) will do the job in nearly every situation. The same goes for dollies. Body dollies are used to back up the metal being shaped using a hammer. They're heavy blocks of hardened steel that come in various shapes and sizes. A general-purpose dolly usually incorporates three or four different contours into one tool, which allows for almost unlimited applications. Another handy design is the toe dolly. This design is a rather thick, nearly rectangular dolly with two straight edges and two rounded edges, each with a slightly different radius.
Body files are normally larger and heavier than the standard metal file you're used to. The double-sided, flat files are used for filing and shaping metal, as you might imagine. Stepped flat files are called "slap files" and used as their name implies (slapping an area of sheetmetal backed by a dolly). They stretch shrunken metal, and highlight spots that need hammer-and-dolly work (though, honestly, this is one tool that I've yet to really master).
Next we'll be focusing on the shop airsupply system, compressors, and spray equipment. We've chosen to tackle this subject at this point because the air supply system is one of the most important shop systems you'll have to consider. Let's face it, even if your foray into paint and body work is a one or two-time deal, you'll flat always be using air tools of one sort or another-and you'll want those tools to work correctly and efficiently.