Use a light dumbbell in your RT hand and push back making sure not to use any momentum.

Switch


Also get a heavy dumbbell and stand it up on the side of the bench. Lay perpendicular on the bench scooting down so only your shoulders are on the bench. Reach back and pick the dumbbell up and don’t hold it directly over your head. Keep the angle so you don’t rest. Straighten your seams and then Take it all the way down and touch the ground and back up.

Those will destroy your triceps