If all else fails just buy a coke and blow across the top of it. It's essentially the same thing. Will at least get muscle memory built for you. The headjoint practice is really the best thing though, I still to about 10 minutes of headjoint work whenever I'm practicing flute right before long tones.
Bruce Pearson is always spot on with his clear and accurate instructions for beginning players. The only thing that I can add is that I have had good success with beginning flute students by telling them to gently keep the lips together and to let the airstream create the opening.
The common problem with beginning flutists of all ages is that the aperture in the lips is too large creating an airy tone, an inability to hold long tones because air is wasted, and sharpness in upper octave cause by blowing harder to go high. The sensation of blowing across a bottle is generally not recommended since it encourages too large an opening in the lips in my experience.
For anyone first learning the flute playing in front of a mirror is indispensable to see the size and shape of the opening and to tell how much of the hole is covered by the bottom lip.
at one time I owned 3 flutes, an Armstrong 101 (student), 303 (intermediate) and model 80 (pro) - models from the 1980s. I couldn't make the 101 to work what-so-ever. It's embouchure hole was distinctly smaller than the other two models. I guess I didn't have a very good direct and accurate air stream though I sounded pretty good on the 303 and 80.