HELP!!!!!!!!
Arban's. Expensive, but worth the money and it can actually be less expensive than trying to collect a number of other, lesser alternatives, method books, etc.
Rochut (i.e., "Melodious Etudes for Trombone, Selected from the Vocalises of Marco Bordogni". Start with book I. Or find something similar with Bordogni vocalises in it.
On the mouthpiece issue I will not give advice since I like a really big euph mouthpiece.
Also, now that I see you're in Charlotte, get the Tuba Christmas book (www.TubaChristmas.com) and work towards handling either the Euph 1 or Euph 2 parts by Christmas (not difficult). Then DEFINITELY head to one of the Tuba Christmas events in NC in Dec. I don't know if they have one in Charlotte (surely they do?), but I will be going to at least two of the Greensboro, Fayetteville, Wilmington and Raleigh (that one's not an "official" Tuba Christmas) events -- probably dragging one or another euph with me since it scares me to go out in crowds with that red brass tuba. And I can play the Tuba 1 part on the euph .
Gary Merrill
Wessex EEb Bass tuba (DW 3XL or 2XL)
Mack Brass Compensating Euph (DE N106, Euph J, J9 euph)
Amati Oval Euph (DE 104, Euph J, J6 euph)
1924 Buescher 3-valve Eb tuba (with std US receiver), Kelly 25
Schiller American Heritage 7B clone bass trombone (DE LB K/K10/112/14 Lexan, Brass Ark MV50R)
1947 Olds "Standard" trombone (Olds #3)