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.
Back in my small hometown in Texas, some of the more eccentric churches would hold these great tent revivals. Even if we didn't like their particular style of religion, we would still sit out in our cars and watch just for the sheer entertainment value of the show.