Lightroom. Import all photos from all sources and have lightroom MOVE THE ORIGINALS into a new root folder with the following structure YYYY/MM
Keep this folder backed up! It's more important than the metadata catalog but now all the raw imagery is in one place.
Then maintain the lightroom catalog with lots of metadata, including using the facial recognition system for offline person recognition, the flag system enabling a 2-pass deletion review, star system for ranking photos by desirability, and add tags to everything. Go through each filter mechanism and develop a strategy for using each filter.
Use the image gallery filter system to the limit.
If you go through images by date & time captured you can usually bulk tag images much more quickly than if you have to switch between events.
Where do I even begin? What app do I use to go through them all?
I've searched and tried out many apps and I still don't have a good workflow.
I truly don't understand how the pros do it.