German use of captured equipment such a tanks as an example, was only done after crews were trained and even modifications done and certainly well marked as German. After that they were only used to support infantry units without other German Armour and the units were well briefed to expect them.
US troops were known to use the odd German Halftrack, but IIRC they were marked with big white stars and mostly used in the rear areas. Hey it beat walking to be sure.
As for picking up small arms and other enemy kit, under normal conditions a sure fire way to get dead as mentioned earlier. When you see regular soldiers carrying enemy weapons it's usually a sign all is not well!! In combat conditions you want to be one with your weapon not just learning about it!! IMHO
Bob out
