yes decent players can figure out that you can pinpoint players through breath. i do it a lot. i usually just knife the guy while hes planting cause you can hear the beeping. as for killing the other players. check the room whenever before you enter it. peek at the corner if you find the guy. make sure hes far enough that he can't hear you. then watch when he looks away. and if you think you can rush him go in for the kill. as for timing your knifing. i suggest entering into normal knifing matches. thats how i practiced. that way you can time the knifing and you won't get gun down.