From Vulgano Brother - "To bring the chops together, purse your lips together as in just before making a "p" sound, then add the mouthpiece. Don't move around inside the mouthpiece, just play, and probably the results will suck at first. Play long tones with diminuendo to nothing. If you can do that well, try starting notes with a breath attack at the same whisper level. This is hard work, and will take time."
This is a very good suggestion but I would suggest something a little different. A variation which I consider to be more effective..at least after you can do the long tone diminuendo one. Take Clarke #1 and start each one this way. Practice it softly and do it in this order: 13, 12, 14, 11, 15, 10, 16, etc… My guess is you will find it harder on your shallower piece and you should do it on your shallower piece.. It's hard at first but, really, if you're persistent, it takes a lot less time than a lot of other things I've seen and is amazingly effective. All the best! Lex