The only verbal communication I use as the pilot is to call out the bumps coming up, or RR tracks. I'll sometimes announce "post" to get out of the saddle for the tracks, but if I say "tracks" and get out of the saddle, she'll quickly follow suit.
I don't announce braking or shifts; after nearly 40 years of cycling, they just come too automatically. I've often shifted before I've even thought about it.
Luis