"Tri" this. This is NOT a DC routine.
Swissball Dumbell Skullcrushers (that's a dumbell in EACH hand) do as many reps as you'd like but in a higher range of 12-15 reps. Then go straight to tricep pushdowns. Don't lock out. Smooth and controlled reps. 5 cnt up...5 cnt down. Same idea for reps. Once you are done STRETCH! Do the DOGGCRAPP STRETCH. Take a dumbell like a one arm dumbell overhead ext and just let the dumbell hand for about 30 sec each arm.
Repeat for 2 more sets.
Last thing:
JM Press or Rev Grip Press for high reps. 1 set. 15+ reps. Stretch. If you hit 30 reps great.
There is nothing magical about this routine. Just another idea. Skullcrushers are the best tricep exercise that I know of. I totally recommend them. The swiss ball is just more comfortable than the bench.