This is what I found. I will get a pitcher to try this during his bullpen and see what happens...
There are two ways to grip a no seam fastball. The first is to place your middle and index finger together on one of the horseshoes. Without touching the seams, place your thumb on the other side. The three fingers used will make the letter "C".
For the second grip, take your middle and index fingers together and place the tips right where the horseshoe starts to close off. Your thumb will end up on the other horseshoe, but it won't touch the seams. You shouldn't apply as much pressure in this grip as the first one.
Since you throw this just like a two-seam or four-seam fastball, sidearm pitching is out of the question. The various overhand and three-quarter release pitching styles are best suited to throw a no seam fastball.
Try moving your thumb to different points underneath the baseball to get extra movement. Placing your thumb in different areas on the ball will make it move laterally in either direction and rise, as well.