Gentlemen,
Respectfully, handling and durability won't be an issue. 
This method calls for the Alclad2 Metalizer to be "Sealed" with a durable Clear Coat. The suggested choices are either Alclad2 Aqua 600 Klear (water base) or Alclad #310 Klear (solvent base). Once sealed, the cars may be handled regularly (although preferably with clean hands).
http://alclad2.com/finishes/aqua-klears/
So far the units that I metalized back in 2005 have been handled considerably and still retain their sheen, gloss level with no damages to the surface.
The intent of using Alclad2 in our hobby is to duplicate the natural metal finishes seen on prototype stainless steel rail passenger cars. It's difficult to do this with silver paints.
The basecoat color influences Alclad's appearance. Hence, we can create stainless steel finishes that look new, aged but in good condition, or worn out.
In addition to sealing, the clear coats tone down the sheen. So if you feel that your finish is too shiny, just add additional coat(s) of clear until you achieve the appearance you want.
For those that want very subdued finishes while maintaining the natural metal appearance, Alclad2 makes clears in Semi gloss, Matt, and Flat finishes (see the link above).
Forgive me for sounding like a salesman, as I don't work for Alclad. But in the HO and N scale worlds we've been excited about this and as I result I've received emails a while back from fellow modelers in the larger scales asking questions about Alclad2 and its applications for trains. For me it's been very enjoyable as since the 1980s, I had fantasized about having my SS passenger cars appear as if they were constructed of stainless steel. Even the bright silver paints turned me off as they did not look like the Budd cars I grew up riding in.
Photos:
The Sleeper is finished in a "worn, but good condition" appearance.
The Baggage-Dorm is in "Well maintained/good" condition.
The Diner (hard to tell with the photo) is in "Excellent" condition with a high reflective surface. With the diner, normally this would be the appearance applied to cars that are new or less than 5 years old but I wanted to have a sample with a "new finish".
As I mentioned earlier, you can basically "Dial In" your appearance with the satisfactory feeling that it will still look prototypical.
