Use heavy negatives on the dip machine for triceps. I absolutely love doing these. It's an effective, safe way to overload your triceps with heavy loads.
Have someone help you do the concentric portion of the lift. Then do the eccentric or negative portion by yourself. Take a few seconds to lower the weight.
I've been called a wide variety of names over the past couple of years. These names have ranged from "guru" to "cheater." Frankly, I don't give a damn what people call me. The bottom line is that I get results with my athletes.