AH rhymes with Saw ٠ UUU rhymes with Too or OOZE.
AAAAHHH-OO-OO-OO-MMMMMMMM
This is the correct/standard way of way of vibrating AUM. You should be able to feel the AH in the stomach, OO in the throat, and MM in the head.
Maum, Thaum, Gaum etc. are vibrated similarly.