Use a flat iron to keep them sleek straight. Or you can also use the flat iron to bend the end of your bangs slightly inward. Depends how you like your short bangs. Rihanna uses flat iron to keep them straight.
Add shine spray to enhance the look. Its a must for dark hair to reflect the light. Finish by using very small amount of styling paste or wax in palm of your hand. Rub it with your finger until its warm up and then play with the end of hair strands, specially in bangs, behind the ear and nape to shape them.