Heres a very informative video of how Edinson Volquez throws his change-up
he taps the ball with his thumb at release
it also shows his two seam grip
I like how he explains it as being just a simple grip and just throwing it. the key is just time and practice to get the feel with the control of it.
Yea I actually throw my changeup like this and it was the easiest changeup for me to learn and throw because its basically a two seam fastball. You do need big hands to throw this pitch in order to get your outside fingers under the ball. I love this pitch though, it gets great movement and drops off the table