I recommend the REKA kit... you stick one end up a nostril (hopefully your own!) and poke it through until the little, orange foam ball (well soaked in soap) enters the sinus. By now the other end should be out your ear.... one smooth pull and everything should be fine!
OK... seriously... I've been experimenting with my own tone lately too... a little bit of an adjustment "here", a hint of relaxation "there".... and "bingo"... my trumpet choir mates say "Holy cow.. what did you just DO!?" It is rather amazing what you can accomplish by listening to your SOUND rather than concentrating on "the notes", "the buttons", etc. Some self-recording helps too. The other thing that's been different... now that summer is here (well, almost)... is that I've been able to go back into my garage (unheated) to practice. The garage has a very "live" sound to it to the extent that I can actually fool around with my sound and "hear" the instant results. I dunno for dead certain what exactly is causing the change ... but I like the results!