Try these things:
Blow like you're blowing out a candle.
Now blow downward like you're trying to make the air hit your chin.
Now play like that, trying to hit your chin. For most people, that will work. Don't "try" to buzz, just get the feeling of freely blowing air downward.
Just a question, if the op happend to be a person who place the mpc low, should he still be blowing downward?