I don't watch much model train stuff on youtube, mostly real trains and of that mostly Virtual Railfan cameras. But I do love anything by Tom McComas.
I did watch a great video of the Lionel North Carolina office the other day. They showed how they are assembling some freight cars here in the states and actually using printers to put graphics onto cars (custom print cars where you can put your birthday or a family members name and picture). It was super cool.