Over the last year, I've had occasion to refinish a few rifles and pistols with a spray-and-bake moly finish. Based on a tip from an AGI gunsmithing video, I use Simple Green to degrease the gun parts prior to coating them. Just spray on the SG, scrub with an old toothbrush, rinse in warm water and dry with compressed air. It works great.
However, I wouldn't use it for routine maintenance; only if the weapon is really, really, grungy or if, like me, you are planning on refinishing it. I'd be a bit reluctant to use it on any gun that wasn't completely stripped down to itsy-bitsy parts that could be quickly and completely dried. You wouldn't want any water to get trapped in cracks and crevices and start it to rusting.