django: exclude models from migrations
You have the correct solution:

used the managed=False Meta option on both Models

It may appear that it is not working but it is likely that you are incorrectly preempting the final result when you see - Create model xxx for models with managed = False when running makemigrations.
How have you been checking/confirming that migrations are being made?
makemigrations will still print to terminal - Create model xxx and create code in the migration file but those migrations will not actually result in any SQL code or appear in Running migrations: when you run migrate.
In my django application (django 1.8) I'm using two databases, one 'default' which is MySQL, and another one which is a schemaless, read-only database.
I've two models which are accessing this database, and I'd like to exclude these two models permanently from data and schema migrations:

makemigrations should never detect any changes, and create migrations for them
migrate should never complain about missing migrations for that app

So far, I've tried different things, all without any success:

used the managed=False Meta option on both Models
added a allow_migrate method to my router which returns False for both models

Does anyone have an example of how this scenario can be achieved?
Thanks for your help!