Here's what you can do.
You'll need a a straightener, boar brush, and hairspray.
Heat up the straightener and take a bit of hair from the bangs. Pull the hair through the straightener in the direction you want it to stay, but instead of just pulling it straight, pull it upwards and around the straightener as you pull - almost like a curling iron (but a curling iron wouldn't have the same effect). Make sure you pull upwards! This will help with the poofing.
While the hair is still hot, quickly take the boar bristle brush and brush the hair - from underneath - into the style you want.
Do the same thing - straightening and brushing - with piece after piece until your bangs are all done.
Next, hold up the hair and spray a bit of hairspray on the underside, at the roots. Wait a few seconds for it to sink in, then brush from the roots outwards. Repeat until it stays!