What are the habbits of succesful Trombone / Trumpet Doublers? There are people past & present that can play both instruments well. Trombone shorty, Mic Gillette, Maynard Ferguson, James Morrison are a few that come to mind. I offen wonder if they practice switching between instuments, and what they work on to build and maintain both embouchures without affecting either one. Any thoughs or advise?

Practice enough on both to stay proficient on both. When practicing, switch randomly between the two on some days. On other days, just complete your routine on one, and then do the same for the other. You don't necessarily have to practice the same amount on either as you would if you just played one instrument, since there is a commonality/overlap between them. And pay attention to fatigue. Playing a brass instrument isn't weight training for the lips; fatigue is more harmful than many players realize.