Dips and close grip bench are good, but by only doing these two and not doing extensions you are likely to end up with an imbalance to the long tricep head which really finishes the overall look of a full tricep off. Cables, IMO are some of the best equipment to isolate the triceps with as they allow constant tension through out the entire movement where free weights may not allow.Any type of extensions murder my elbows regardless of rep range. The only "extension" i can do is more like a pullover hybrid where i bring the ez bar downy way past my head (which hangs off the bench) and then bring the bar up short off 90 degrees over the torso. It hits the long head really hard and is much safer on the elbows.
This may sound wrong but adding a bit of shoulder movement into "isolation" movements for the triceps don't just make them safer on the joints, it allows you to handle heavier weight for more growth. The elbow joint is not really designed to move in isolation. It's a very unnatural thing to do.
And then there is dips and close grip bench. That's all i need for tris. I don't see the point of using cables.