Clint McLauglin talks about the "Tootpaste method" in his books (
www.Bbtrumpet.com).
For me breathing is simple, when I have to play I breath in and play. I don't see why you should do it otherwise. It's the same with talking or singing, it's a natural proces.
But I breath different for different sound colors or styles. If I play with a classical broad sound I only breath low. If I have to play a tutti in a big band as a leadplayer I create more aire pressure with something like Bobby Shew's "wedge". The sound gets more overtones and more projection.