Lightroom :: Filtering Library By Collection Status

I've been using LR for adjusting photos for about 6-8 years now, but have just recently gotten time to start better organizing my stuff. I have about 40,000 images that mostly have keywords and descriptive file names, but are generally without ratings, color labels and are mostly not in collections. I must admit that there's a lot of junk in there (duplicates, mostly) that I have to purge. I can probably work it down to 10,000 images. In addition to putting ratings and labels on things, I want to sort them into collections, but that task would be easier if I knew which images were NOT in collections so I could concentrate on them and work that set down. I don't see a way to set up smart collections to show images that are not in a collection. It appears that the smart collection criteria can be selected from whatever text selection criteria are available, and I don't see inclusion in a collection as one of them. I also don't see collection status as one of the metadata items that could be used to filter things.
 
In a previous thread from 2007 I found the following workaround:
 
Clear the quick collection and set it to the target collection.In the library view, select all the collections. Select all the photos.Go to the catalog and view all photos.In the Edit menu, click on "invert selection".That selects all the images not in a collection. Pressing B puts them in the quick collection.
 
The only problem with this is that when you select an image from the quick collection and place it in a collection the image remains in the quick collection. In a smart collection filtered by collection status (not in a collection) it would disappear from the smart collection when it goes into a collection. So it would be much nicer if there were a way to filter for "not in a collection" for a smart collection or even in a metadata filter.
 
The above workaround does work, but you will have to refresh the quick collection whenever you lose track of which images you have placed into a collection.
 
Of course, the best solution would be not to get into my position in the first place. Always dump the junk out of the catalog and place all the keepers in appropriate collections.