I use 2 different warmups, first is for rows, deads, or bench depending on the day, 2nd is for squats on leg day.
Bar x 12
85 x 6
115 x 5
145 x 3
165 x 1
185 x 1
205 x 5 workset

or

45 x 5 x 2
95 x 3 x 2
135 x 3
185 x 3
225 x 3
275 x 1
315 x 1
365 x 1

Hrd, I wouldnt do the extra set afterwards. Just do a stretch. Use either a weight or bodyweight. My brother and I do the DC stretching. 0311 has it in his dc writeup. It is a good burn holding the weight, or holding your bodyweight for the minute or so.

The time to warm up is not long at all, those 10 sets on leg day are done within 15-20 min, because there is only 1-1.5 min rest between sets.