After trying many different ways over the years to control all my Metadata, i find the best way is to upload to pond5 first and use them as a base for other agencies. Their back office system is very easy to use and you can save templates to re-use for similar content. The main reason however is they allow you to download a .CSV file of your metadata which is then easy to give to other agencies as needed.

im sure there are better/different ways, but this currently works for me.