How do I map SSIS 2012 Package Variables to Parameters?

I have created multiple packages that use variables to assign Connection Manager Expressions such as Connection String. However in the new SQL 2012 Project Deployment Model I don't seem to be able to configure these variables. Would I therefore need to create these Parameters for the Environment and map them to specific Package Variables? Is this even possible and how is this done? This link describes configuring the Parameters, but not associating to **package** Variables. Further to this, it seems I *could* set a Varaiable Expression to be a Project or Package Parameter, however this seems a bit convoluted. Perhaps I should stop using Variables altogether? ----- Update: I've now cut-over to using Project-level and Package-level Parameters (instead of Package Variables) when I need to modify per-environment settings such as file paths and connection strings. Perhaps this was the intent from MS: any best practice advice is of course, still welcome.