A turning point in my progress as a horn player happened soon after I found some warm-ups that worked on wide-interval slurs and improved my flexibility. One I found at a master class from Bernhard Scully, the horn player for the Canadian Brass:
This pattern (all slurred) continues two more times, radiating out from middle C in progressively larger intervals until slurring between three C's at the end. Like any new warm-up, starting slowly and being a perfectionist with yourself lets you grasp what you need to do in order to hit the intervals correctly. This warm-up can teach you how to change your embouchure more quickly and accurately, and improve your sense of interval in other areas of playing.
A second slurred pattern I came across outlines a popular slurred arpeggio pattern from the trombone world, but takes it one step further:
This is also all slurred, and really works on smoothing out large-interval slurs. It should be played on all horns. Like the previous exercise, this one works specifically on being able to change your embouchure and mouth shape quickly and accurately.
These two exercises noticeably improved my playing. Maybe they can help you!