Clarke Technical Studies for Trumpet, Fourth Study, Exercise 66 play-along video with music notation.
These exercises were written to overcome the difficulty of producing the whole tone trill on the cornet.
With slow and careful practice, the mechanical imperfections found in some instruments can be surmounted. The most troublesome intervals are B-natural to C-sharp (Ex. 71) and C to D (Ex. 72).
The fingers and lips should remain flexible throughout this study. When you have mastered these exercises as written, single and then double tongue them.
Practice Etude 4 until you can play it in one breath.