these are awesome. I just started doing them two months ago and I have seen a difference in my triceps. they have made the lower portion of my elbow thicker and my triceps fuller.
best way I can describe doing them, is to lay on a flat bench, or incline(be sure to have a towel underneath your neck for incline. your neck shouldn't be involved in this exercise by raising your head with the weight). press the dbs up, and then lower the weight to your upper chest/collarbone area. then extend up with your elbows perpendicular to your body. throughout the whole movement, the dbs should be touching for maximum effectiveness. I have found that if I squeeze my shoulder blades together, it isolates the tris more. hope this helps.