Get any pitch going with the buzz, don't worry about specific intervals. It's a lot easier to sing higher than the buzzed pitch, for most people at least. Do it on the mouthpiece alone, and when you get a good, sustained sing/buzz, put the mpc into the horn.
There aren't any magic words, unfortunately, and no real universal tricks. But, once you get it, it never really goes away.
Once you've established your ability to play and sing, THEN start working on specific intervals, and getting them in tune. (That gives YOU a hobby


