How do I share Apple Photos without iCloud?

I want to share Apple Photos libraries, from different user accounts, but on a single machine i.e I want to see another user's library and allow them to see mine. I don't want to use iCloud because a) my internet connection is slow and intermittent b) my library is very large c) I only want to share on one machine and c) I don't want to create new albums solely for the purpose of sharing.

Can anyone suggest how I might do this?

Ian