I'm far from being an expert with UVW unwrapping in Blender. So don't expect this answer to be as short and useful as the previous one
When doing unwrapping, I always do it by using "Project from view" (UKEY, choice #5) I do it several times, a subset of each object at a time. Then, you'll have to merge vertices shown twice (because selected twice on two different faces) or more. To do that, use Ctrl+C to activate automate selection of multiply-shown-vertices, then V to merge them. Actually it won't merge them (just place both at the very same location) so you'll have to stick using the Ctrl+C feature (otherwise use Alt+C to stop using it)