During the last 20+ years I grew close to Reb Mendel.  Every so often he would ask me halacha shaylos. I recall in particular: his feet muscles were paining him- if he on shabbos he can ice to alleviate pain;  doing physiotherapy exercises on shabbos; spreading ice (which might be considered a food) on ice walkway (and then walking on "food"); using a cane on shabbos (when he doesn't rely on eruv)....He would slowly walk over to me in yeshiva and ask me to read the small words in these seforim to see if it is mutar or ossur...occasionally asking that I should show him the psak and if it is l'chol ha'dayos.

Around 12-15 years ago, a sophisticated professional lady who wasn't religious brought me her mezuza and asked if it is Kosher or needs replacement. To me, it was obviously possol but I told her to ask a Sofer. My initial thought was to send her to Reb Akiva Fliesher, an American born sofer with a good English etc. But then I decided to send her into the "fire" - to go to Reb Mendel. I told her a bit about him and that his English isn't  the Queens English. What could go wrong? At least she will meet a chassishe yid! 

She brought him the mezuza. He look one glance at it and said, no good! She was taken aback. She expected him to examine it at length before making a determination. She immediately asked, how can you know that it's no good - you barely looked at it?! Reb Medley put down the mezuza, looked her in the eyes and asked her what her profession is? She told him. Then he said, "I don't question you in your professional expertise and you shouldn't question me in mine...when you become an expert in my profession then you have a right to ask if you may ask."

When the lady told me this, I started to make excuses for Ren Mendel. But she stopped me and said that is exactly what she needed to hear.

She always questioned the opinions of rabbis including the entire Torah shebal peh. How do they know what is a melacha on shabbos, shchita...he taught her until she becomes an expert she must accept without question.