I have been playing bass trombone for about a year, and my problem is not positions or intonation, or air, but how to get a good big band (jazz band) bass trombone sound? I mean I listen to jazz bass trombonists both solo and within bands. And they have a specific tone, that's blattier than say a bass trombone in a concert band or orchestra setting. Any tips would be apreciated
Use a shallower mouthpiece. On any brass instrument, a shallower cup on the mouthpiece will allow the player more range (it's easier to switch partials; I'm actually not sure why, but I think it has to do with adding backpressure), but the tradeoff is a "blattier" sound; less mellow, harder to blend in with a large group (because that backpressure makes it easier to "overblow" the instrument), so classical teachers will encourage a deeper cup. Definitely avoid the long cone-shaped "mellophone-style" mouthpieces if you're looking for blat.
Also, try closing your mouth/soft palate a bit. If you've been trained in "singer-style" breath control (where you control the breath with your diaphragm, not by closing off your throat), you get a very nice open sound that's exactly what your classical brass teacher wants. But, your jazz teacher may actually tell you to clamp down a bit for stylistic purposes. Just don't totally forget the good habits of classical technique.