To achieve the effect you're looking for, where rotating the hand moves a "piston" cuff bone up and down the arm, you can use a combination of transform constraints and possibly IK constraints. Here's a general approach:
Transform Constraint: Use a transform constraint to link the rotation of the hand bone to the translation of the cuff bone. You can set the constraint to affect only the Y-axis translation of the cuff bone. This way, when the hand rotates, the cuff bone will move up and down along the arm.
IK Constraint: If you want the cuff to maintain a specific orientation or follow a path, you might consider using an IK constraint to control its movement more precisely.
Relative Movement: Ensure that the transform constraint is set to relative, so that the movement of the cuff bone is relative to the arm's position, allowing for animation of the arm moving around.
The crank-slider rig example you mentioned involves using a transform constraint to mimic the translation of a rotating bone, which is similar to what you need. You can adapt this method by ensuring the constraint is set to affect only the desired axis and is relative to the arm's movement.
If you need more specific guidance, you might want to experiment with these constraints in a simple setup to see how they interact and adjust the settings to fit your animation needs.
