stchasking

I am going to add 2 pence for what it is worth.
Contract the meat of your lip toward the center of the mouthpiece. Get cushion under the mouthpiece.
It works for me. I have been trying to understand the Louis Maggio method for about 15 years and this is the best I can say without someone teaching me.

I have found recently that playing low notes with my borrowed flugalhorn has greatly improved my playing the next day. Call it a warm down or whatever but it has really helped me. I use the Chas Colin suggested above.
I use a Bach 3D in both the trumpet and flugalhorn. The flugalhorn is a lot easier to get the pedal tones with the D cup mouthpiece compared to trumpet.