Ohhh…yes, very nice looking grungy thingie Airflamesred. I’ve looked quickly through the Bible and I can’t find any mention as to why reading alpha information should be different between the terrain editor and the texture editor in 2D mode. The terrain editor is more straight forward and intuitive and more in par with other 3D programs in keeping with height map translation protocol.

As for applying texture I would say in this case to get that random arbitrary scattering effect of the dents and scratches it’s best to spray right on the model but for more precise and particular placement for things such as lettering as say a patent logo I would go with the more work intensive method of exporting the uv map to an external image editing program. Yes I’m familiar with this CG-Talk tutorial you link to and I think it’s one of the finest .  He also has this tutorial in PDF format and other free props at his website (download section) which use to have more tutorials but he’s taken them off…sigh.

I’m not sure what you mean by copying directly to the bump channel either. Whenever I try to past an image from clipboard memory into the output channel in the picture lab or the terrain editor it pastes fine but if you mean into the texture lab bump channel it doesn’t paste.