The method: to digest the potion. The outsider must behave as prescribed by his stage until the power becomes part of him. Until the potion is digested, the bearer is vulnerable: the power is already there, but there is no control over it yet.
The roles of the path are associated with risk and stakes: the bearer puts the outcome on the line again and again and learns to live with what comes up.
The method remained known to few for a long time: the church hierarchs were in no hurry to reveal it, and many outsiders rose blindly, paying for it with their sanity.