The nice thing about playing other brass instrument than trumpet (like horn, euhponium or tuba) is that one get in contact with other literature than trumpet books.
What have struck me is that people playing other brass instrument than trumpet are more interested in their "brass cousins".
On page 69 in Brass Bulletin No. 102 - 1998 there is a picture of Maurice André, Roger Bobo, Stella Stamp, Frøydis Ree Wekre and James Stamp.(It's an article by Stamp pupil J-C. Wiener).
Roger Bobo is a well known tuba soloist. He has written a book called "Mastering the Tuba" (Book 1 - Fundamental Exercises), Edition BIM 1993.
It is a pity he called it that because it is a book for all brass and most of the exercises are written in treble clef.
I have written a small article about that book:
and there I say:
"The exercise called "Stamp Modification 2" (page 36 - 39) is in both Bobo and my opinion "perhaps the greatest" of all the Stamp exercises. The modification or supplement that Bobo have done to this exercise is maybe good enough reason for any trumpet player (who already know Stamp) to get this book, ASAP. This exercise has been expanded to A above high C, starting from the low G and then returning down to pedal G - which encompasses 5 octaves."
Get it ASAP (BIM takes credit cards), I have placed a link to BIM in the article.
I have earlier mentioned the book by Wekre:
"Thoughts on playing the Horn well". She also uses some modified Stamp exercises. But in that book is also a great mouthpiece exercise that Bobo also uses, called "Octave Glissandos".
I have modified it to trumpet and I use in may warm up and it works
great for me. Here is the URL to the exercise:
I start on pedal C and slur up to low C then I make a slow glissando down to pedal C again. This is first part. Second part start on low C and slur down to pedal C and then make a glissando back up to low C. Rest. Then I start on C#, rest, then D and so on as high as I can play comfortable.
Additional one can do this on the lips (and watch the movement in a mirror). Also try it in the horn (quite difficult - but good practice).