Mr. Surfacer can also be applied by brush to fill in join lines, small gaps, etc... on aircraft models (or any other model for that matter). You can see this technique used here
Jean-Luc's Ki-45 I haven't tried it yet myself for either armor texturing or seam filling, but having just picked some up at a local hobby store, I will try it out soon.
As to who Mr. Surfacer is, I think he must be Mr. Color's brother or something.