whats the smoke coming from?

I cant imagine you being able to touch the brake parts without frying yourself if the brakes were at fault. Also gear lube or brake fluid would not necessarily smoke unless you were on the brakes often enough to get them really hot. Maybe the parking brake is dragging just a little. If so the wheel would be hot. Something is missing here. If the tire was rubbing it would be pretty obvious.
Maybe it is low on gear lube, just a stab in the dark, but hey. If it were me I would try to locate the source of the heat, instead of what the smoke is composed of.