Just about every pass when he's under center is a 3 or 5 step drop. Unless he's through a quick pass to the flats, it's always a 3 or 5 step drop if he's under center.
This thread makes me think of an old video I saw a few years ago of Walsh working with Cool Joe on his drops. The video was really good and I believe the whole piece I watched which included this clip was about Brady and his footwork and how it mirrored what Joe and Walsh did.
I like most dont pay close attention to his drops but we all can see how uncanny his footwork in the pocket is evading rushers and I would assume his footwork in his drops would be equally as good if not better as there is no improvising needed just on the drop like overall pocket presence requires.