Well, I tried handling trains with gloves at one time and quickly determined that doesn't work well as details can be easily snagged by the gloves.
My solution is to wash hands with soap and water before handling trains. That keeps the oily fingerprints off them. Sometimes I go one better and use a little rubbing alcohol on my hands also but let them dry before touching any trains.
Oily fingerprints can often be cleaned up with a Q-tip and a little bit of soap and water, followed by a dry Q-tip to remove the water so you don't get any spotting.
Sometimes I will use a little bit of high end car wax on plated and clearcoated finishes to remove or blend in any irregular shiny spots again with either Q-tips or soft cotton cloths. I do not use this on Athearn plated finishes as their clearcoat is easily marred or chips off too readily.
John
A bit late to the party........
I've preferred kits but did have a number of Walthers "RTR" passenger cars. They were all well packaged and never a problem. When I sold them two years ago they went back into the original packaging and the buyers were all pleased.
Somewhere along the line the OP's packaged cars were mishandled, but having so many hit one buyer begs more questions. I won't get into that.
What I will say is I learned over many years that the Athearn, MDC, and similar kit built cars were pretty much built for regular layout use and they held up well.
The "craftsman" kits I built were full of fragile parts and did best with special handling, on sidings, or in display cases. The thing is, if you want the full details, you have to give them that special care. I look at the pics Wayne provided earlier and they are a good example of proper storage.
That said, you just can't properly store delicate items in their packaging and then "bounce them all over the place" or "stack stuff on top of them" and not get damage.
Hey, for what its worth.......
ENJOY !
Mobilman44
Living in southeast Texas, formerly modeling the "postwar" Santa Fe and Illinois Central
I have had a few hit the concrete in my old place, was surprised I had little damage and on only one car and this accident was from me fumbling. As for regular damage, most has been caused by mishandleing or improper instalation of parts.
https://www.newcars.com/mini/car-dealers/delaware
I've been trying to sell off a pile of mostly old IM, Tichy, Red Caboose and similar assembled freight cars kits for a friend, who assembled them with whatever CA glue Dollar General had on sale. They shed parts like crazy, but that doesn't sound like your problem.