I received an e-mail from Adam Sadler at PP regarding my 2 questions. Here are the questions and his responses:
Rule Question:
1) Heizinger's Hermetica Occulta requires a non-Obscura Korps figure to make a mental dual to enter a circle on his path. Only one test allowed. Do you need to make a mental dual if you are already on a circle on his path and wish to move to another circle on his path?
2) Main rule requires you to spend an action to use equipment. Hoss' Reichdoktor seems to be activated during another freindly character's activation. Is this correct or does Hoss need to spend an action during his activation to put 2 successes on another friendly character?
Rule Response:
1) Yes, a character lacking the Obscura Korps symbol must always test to enter a circle on his path.
2) The Reichdoktor ability does not require an action.
It does seem that you are limited to one test to get on Heizinger's path and that is as far as you get.