Easiest Gun Wheel Guru method by far!!!
Go to 10-0 Glide Time. There will be a checkpoint. The top of the screen will say "Head for Herkas HQ". The male dude will say "We are getting closer right?" The female will say "Were getting closer". You will be heading around a corner with a sniper rifle (X35 long arm) in front of you. Run around the corner and sprint toward the enemies. Hug the right wall and enter an alcove behind some glass. run to the end. One or two Gun Wheels will follow. Damage the gun wheel and mindslave it. Quickly enter the gun wheel before it leaves. Now if you just be patient and aim between the glass barriers you can easily kill 10 or so guys without a problem. most will be focusing on the main characters. If you die, be sure to separate your two characters and purposely die apart so there is no auto heal. Rinse and repeat. I got all 20 kills in 3 tries.