There are tons of drills you can do.
1st shot accuracy drill: At the start position you turn ad raise your marker, firing one ball at a target about the size of a paintball box. Once you can hit it consistantly move the box farther back and try it again.
Gatorade bottle snap shot drill: one gatorade bottle (32 ounce or larger) on each side of the bunker about 1 foot away. you have a player in a mirroring bunker with the same set up. You come out shoot one ball at the bottle then come back in. You have to hit both bottles before you can engage the other player. Only one shot per exposure. This gets really tricky when your mirror has shot both of his bottles and you still have to shoot you bottles before you canshot at him.
Duel: start on oppisite corners and run to the 50. While running you are tryingto shoot the guy on the otherside of the field doing the same thing. Stop shooting at the 50 and keep running to the end of the field.
Zig-Zag: set up cones in a zig-zag pattern and shoot at the next cone in the line while running to the cone before it. When you get to the cone switch hands and fire at the next cone while running toward the cone you just shot at. A 6-8 cone zig-zag will wear you out after 15 minutes.
There are plenty more.