Using Coach Poliquin as a guide - Dips then close grip bench are two of the best triceps builders. If you are looking to use a lighter load - then slow the lifting cadence (4 to 5 seconds on the 1) negative 2) concentric)), followed by utilizing a 2 second pause at the "bottom" of the lift (bottom being defined as point in the lift prior to the concentric portion).
Basically getting rid of momentum (pauses) and increasing time under tension (cadence) will make any lift harder, hence lighter load.