basically, it is a metal glue that is used instead of welding when attaching body panels from the factory (usually roofskins, doorskins, quarters) in most cases it is just as strong as welding the panels on.
here is the fusor product sheet.
Metal Adhesives
any more q's...ask away.
yes some clears have a matting agent that can be added. I would just use a prepackaged satin clearcoat, rather than adding matting agent to a regular clear.