amtrpt

Roy,
First of all try to stay relaxed, especially the back of your tounge. The tounge is a fairly large muscle that extends a bit down your throat so throat tension will really slow you down. I like to practice actual speed in two ways. First go to the Arban multiple tounging section and start working on those studies single tounged, especially the easier ones at the beginning. Make sure that you are playing them slow enough at first to focus on relaxtion. Gradually start stretching yourself with the metronome speed. The second way I like to do it is without the trumpet. Take those same exercises from the Arban book and do them while you are walking or driving. This is a great way to practice exercising your tounge muscle and it also saves chops a bit.
Hope that helps.
Best,
Andrew