From my understanding you do two warm up sets- one at 10-12 reps...another at 8-10 reps then one working set where you do a drop set or if you have a spotter you do negatives/forced reps.
So lets say its chest day... i first do incline db press. I do my two warm up sets... then my working set. Then I move on to flat db press... it seems redundant to do another two "warm up sets" doesnt it? And if im doing two sets of a moderately heavy weight isnt that taking away from the maximum amount of weight I could be doing in my working set?