I am of the opinion that the greatest of all teachers is he who is not conscious that he is teaching. Help me out here  

I agree. It's a person being themselves, without want of themselves, without want to change or convince another, without ego.

Hi looking glass! If we are correct, the opposite must be true for one who learns of the Spirit.? lol

Hi lighting. I don't believe the opposite must be true of one who learns of the Spirit. To me it is the same qualities.

I don't think there is an absolute answer.  Sometimes the greatest teacher can be the one who has the largest ego, who has done the most despicable thing that you could ever imagine.  Something can get triggered inside of the person who is learning and they make a huge change in their life. I remember a Jimmy Cagney movie (that ages me).  He plays a man who is in prison, sentenced to die.  A strong fearless person who plans on showing everybody to the bitter end that he isn't afraid, he can stand up to anything.  He is a "role model" for the kids in the neighborhood who want to be just like him.  The priest in the neighborhood comes to the condemned man and talks with him about the legacy he is leaving all those kids.  Does he really want those boys to end up like him? In the end he goes to the "chair" to die, kicking and screaming, playing that he is terrified.  

The greatest teacher is the one who is going to get thru to us. We never know what that will be, how it will get into that part of us that needs to hear and learn and grow.  
The teachings from wonderful, powerful, spiritual teachers can be twisted into unloving demonic things when a twisted mind misuses the great love filled teaching.  

It is in each person, here to learn and grow, work out karma, share and live, to take in the teachings around us from nature, from the animal kingdom, from the stars at night, etc  and apply them into our lives.  Everyone and everything is the greatest teacher at all times, depending on what each individual is here to learn and how open they are to receive the teachings.
Just my opinion.  

We are all students and all teachers.