Chef encrypted databags or a similar approach where the environment variable is encrypted on disk and decrypted at runtime. Obviously your deployment nodes eventually need the secret in plaintext and all end up with the key, but at least the information is encrypted at rest (for example in your source control, a common source of breaches).

It doesn't seem wise to share secrets amongst developers (especially new ones) to me - that sounds like a recipe for disaster. GitHub accidentally deleted their production database by giving developers access to production secrets on their local machines a few years ago - regardless of how much you trust your people it's not a particularly solid plan.