Last week, our post talked about warming up the voice before singing. This week Lisa Popeil has an exercise to help you find or define your upper and lower ranges. She uses an "aw" sound that has, in my view, a bit of a twang. Listen and notice that her sound has more of a throat sound. My suggestion would be to drop the jaw a bit more and make the sound more as you would when you see a cute baby - "ah".
Then, for the upper range, Lisa pulls out the lip trills or "bubbling" discussed last week. This does work better I think. Is there any reason you couldn't use the lip trills for the lower sounds? Try it and see what you think.