If someone is DOWN, always Shoot someone Quickly before reviving them, can't stress this enough, COMBO is priority, then get them up. If my team mate is down, I usually get magnum out, pop a couple kills then Revive, Use the spray you collected (there are 2 sprays on Mining Depths/ steel beast and 1 on urban Chaos) to revive people instantly and not loose combo, Spray is WAY better than giving them a pill, which you will usually drop your combo, you will definetly drop combo if you Don't shoot someone quickly before reviving and Don't use the spray like i said..