My experience is in S&B construction, but I can tell you that the aluminum siding people there say that the gaps where siding overlaps are ESSENTIAL for allowing condensation inside the walls to evaporate. I would not seal those up with coating.
The rubber around windows, etc. expands and contracts at a different rate from the aluminum, and more than the glass. A coating on it will likely fail sooner (lots of cracks) and, if you coat the glass too, will crack all along where rubber meets glass.
Chrome should be fine if you sand the heck out of it, as stated above. It does tend to be located on the wear points of the vehicle.
Auto shops are great urban camo. For truck campers, I would think a residential neighborhood where other pickups are parked on the street would be good, too. Me, I like the neighborhoods where you can't go a block without seeing my model of van :).