Train the long splitting pass through a narrow gap, and the short pass that sets it up. Players have to strike a sixteen metre ball accurately enough to find a gate under five metres wide, then follow it and be ready to receive.
Set four mannequins in two pairs to leave a gate of about four and a half metres, with stations either side of the wall and one above and below it. The long pass goes through the gate to a player on the far side, who sets it short to the next station. That player then plays the long pass back through the gate the other way. Everybody follows their pass to the station they played to. Two touch throughout, and keep the gate narrow.
The pass that splits two defenders is the one that changes a game and the one players practise least. Passing drills are overwhelmingly played into open space, at a teammate who is entirely free, which trains weight and accuracy in a general way but never trains the thing that makes a splitting pass different: it has to go through a specific gap and it has to be flat.
A four and a half metre gate at sixteen metres is a genuinely demanding target, and it produces the correct technique almost by itself. Players quickly discover that a lifted ball does not work, because a bouncing pass through a gap is uncontrollable at the far end, and that a soft one does not work either, because it spends too long in the gate. What is left is a firm, flat, accurate ball, which is the only version that works against real defenders.
The coaching cue that changes most players immediately is to look at the gate rather than the receiver. Aiming at a teammate standing behind two mannequins naturally pulls the pass toward the mannequins, because that is the line the eye is drawn along. Aiming at the gap itself, and trusting the receiver to be behind it, straightens the ball out.
The short set on the far side is not filler. It is what turns each repetition around and, more usefully, it is the pass that in a real sequence would set the splitting ball up. Following your pass keeps everyone moving and stops the drill becoming five players in fixed positions, which is what it would collapse into within two minutes if the rotation were dropped.
Save it to your private drills, then change the animation, adjust positions, swap equipment, or drop it into a session block. Or start from a blank pitch and build your own.