Skip Second Thing Boss:
There is a garage door to the left of the second Thing Boss's door. Have a team member stand near it and then back up and toss a grenade at them. Your team member will run towards the door which will open, allowing you to run in there with them if done correctly.
Unlimited Flares:
Highlight "Flare" and enable it but don't throw it. When it is low, press Left or Right and highlight another object. Then highlight "Flare" again. It will have restarted and you will not lose another one.
Test Kit Hint:
Don't bother using test kits on your team members since they will get infected randomly and will mutate quickly. Instead save the kits for use on yourself to prove you are not infected.
