I have been doing the lip buzz for twenty years, but only as a warm-up.
Buzz a 2nd line G, "walk" the horn into the chops, "walk" it out, buzz
up to an Ab, "walk' The horn in, etc. It helped me get the 'focus"
going. In collage, I was even doing this without the mouthpiece (straight
into the leadpipe) and achieving a decent tone. Recently, I have
played using only the buzz (if that makes sense). I can pull the
horn off anytime and I am buzzing that note.
Whereas before, I could only hit a dbl G only during warmups (and the very beginning of the gig), I am now playing "peeling paint" dbl A's at the end of the fourth set (and those dbl C's are there as well - not as big, though) without the effort I needed before just to reach high E's.