i have never been in this situation though i can certainly see the appeal from both sides, i think.

i would say that your submissive helper would need to be poised and confident enough to act as she would were you her Master, in order for the new Dom to get a true sense of what it would be like. She would need to have full trust in you in that you would be able to completely control not only yourself in the given situation but also another, and a newbie at that. Patience and understanding would be big. And i think it would be important for her to be able to speak eloquently, with well thought out answers, be good at descriptions and describing her feelings so that she could clarify what she was experiencing at any time.

i am sure there is much more but those things are the first that spring to my mind.

respectfully,
orchid