Great post John. Francis sorry not on Facebook maybe something I should consider. An exercise I do away from the horn is to form an open low C embouchure and then focus on firming the corners and bringing them Inwards. I just practise flexing the corners in a horizontal way. This has help me train my brain to activate the required muscles. This is a good exercise to practise with passive air and the concert hall breath. That way you are training yourself to activate the aperture corners inwards and release air without any air support as if your are playing a passive air exercise. I think the ability to control the aperture corners is the key to smooth and fast slurs.

I can do the slurs but I cannot do them as fast as Greg. As I try to get faster they get very untidy. ie they lose smoothness. This I think has to do with my control of the aperture corners but being fast and smooth in operation. But each day they improve. This is something I think just takes time.