Very nice tutorial! It is indeed a bit less confusing than the one I saw before the nuke (no offence), so I might actually start dropping the eraser tool and try this
As for the "specks" remaining due to cutting a render, I find it useful (especially when pasting onto invisible background) to use Layer -> Layer Style -> Stroke @ about 2-3 pixels and a highly visible colour (red, blue, green, depending on the render) to find the last specks.
Also, even if I endanger myself to sound dumb, I save all my cut-out renders on invis background for later use, so I can resize or re-cut them at will. But then again, who wouldn't
