David, I have applied these whiteboard films wet in the past, but it is a big no no. Especially if it is going on steel. The glue is usually water based too which is another reason you shoud not do it wet, although water based glues can be applied wet in some circumstances. The last one I applied it to went on a painted plaster wall, and all was sweet, but you will have to work hard to remove as much water as you can.
a 6 x 9 on a verticle surface could be a dry application with two people. A horizontal application dry is feasable but difficult without 2 or 3 people to help.
Chrome or Silver poly should only be applied dry.