How do I protect a model that includes custom signals and busses?

I would like to protect a model where internally I have custom busses and signals. External interfaces however are all standard data types. How can I protect the model such that the busses and signals don't show up in the workspace and only stay scoped to the protected model? As I have found to do it now they will show up in the workspace.

[Jeremy Quandt]

This seems promising: How do I create a protected model with hidden variables with a mask that provides additional variables?