Spray on Dirt is a great idea indeed to quickly repaint, temporarily vehicles in military convoys. When moving large convoys through the battlefield it is necessary to conceal his best possible your troops movements.
Today with satellites in space and unmanned aerial vehicles in the sky; there are all eyes everywhere. It is therefore very important to conceal your location as long as possible and hopefully see your enemy before they see you and fire upon them before they know what happened.
The idea of spray on dirt therefore makes sense, however many military tactics advisers say that spray on dirt is an expensive process, requires expert training and adds vehicles to the convoy and personnel to do the job. It just does not makes sense to put more than is absolutely needed at risk in the war zone.
Indeed, my thoughts are to KISS, simple equipment, basic application, fast, efficient and on the go. When advancing in the Modern Net-Centric Battlespace, speed is important. If a piece of hardware, one man submarine, Humvee, even a robotic Sandia