The insight came during the night that hermit "formation" varies from the formation of monks and nuns. Hermits who derive from religious orders and congregations, of course, have the inherent formation, but hermit life involves unique formation by the Holy Spirit.
Since hermits' rules of life vary according to each hermit, the formation is unique. Since there is no novice master or mistress, the spiritual director might take that role, or the confessor, but not in as direct way. No, for the hermit, the Holy Spirit is the One Who forms the hermit according to God's will, and union with Christ as goal.
Much of the formation utilizes the rule of life, unique to each hermit, as the proving ground. Boot camp extends into life career into eternal destiny.
Some hermits may spend years working toward canonical approval; others may discover early on that God wills otherwise, and the formation requires more hiddenness. For all hermits, dying to self is requisite. The Holy Spirit moves in whatever way necessary within the hermit soul to bring this to effective result.
Formation for a hermit evolves moment by moment. Expect the unexpected within a framework of silence and penance.