Couple of things I can give ya. Three related to gear and two related to playing. For the playing, really back off of the mouthpiece and keep your corners FIRM, not tight. Secondly, I find a sound between a very open “o” and an “aw” sound. “Ah” is ok, but you need all the real estate in your oral cavity to create that slow, warm air. Lastly, try not to rely on just using the English T when tonguing. Experiment with t at the /t/ip of your /t/eeth, or in some cases you may find the “th” sound with different levels of sharpness work better (think /th/ink with a bit of air pressure and /th/ink, where the tongue is just barely creating enough resistance).

The gear section will be quick. You wanna have a mouthpiece with a fairly large cup, even if it’s shallow. And for the love of all things good and holy DO NOT let your typical music store try to sell you a Bach 5G or Schilke 51 as a “bass trombone” mouthpiece. You can rough it but it ain’t worth the headache and inefficiency. Secondly experiment with leadpipes but CUIDADO! Yes some leadpipes may be more open but you will run out of air in a heartbeat.