How do I sync favorite photos across devices?

Hi. I have a large number of photos from a recent trip. They have been divided via Smart Album by date. I'd like to review them, selecting occasional photos for possible posting and editing later. To do this, I'd like to be able to use my iPad, so I'm not tethered to my iMac. However, I cannot figure out how to designate "favorite" photos in a way that allows me to easily share my work across devices. In other words, I can "favorite" a photo on my iMac, but I cannot favorite a photo on my iPad and have my iMac immediately recognize that I've done so.

Part of the problem seems to be that the "favorites" button is not available in all albums where a photo might be found. In any event, even manually syncing the "Favorites" album via iTunes merely results in a copy of the iMac Favorites file separate from the "local" iPad Favorites file.

Any suggestions would be greatly welcomed!