Make the Image File Carry Its Own Model Release
The short answer
Commercial delivery is two files: the photo and the signed release. The image file should also carry the release signal in three IPTC fields, so the client's library never has to hunt for paperwork. Model Release Status and Property Release Status each have exactly four valid values; Rights Usage Terms is free text. Batch-apply all three from a release-on-file lookup in one pass before you deliver.
A commercial studio day, run as a single-venue batch, ends with two things on your drive. The photographs, and the paperwork. The model release the talent signed. The property release the location manager initialed. The licensing terms you and the client agreed on in the estimate. Two stacks, image files and legal files, and they travel to the client as separate things that the client now has to keep married for the life of the asset. Commercial photography model release metadata is the thread that keeps them married: a signal written into the image so the file and the paperwork never drift apart.
That marriage breaks. It breaks when the photo lands in the brand's digital asset manager and the release PDF lands in someone's email. It breaks eighteen months later when a downstream licensor wants to re-use the frame and cannot tell from the file alone whether a release exists. The pros I talk to describe the same recurring email: a client's legal team asking, about a specific JPEG, "is this one cleared?"