In this trick every throw from one hand is made Over the top, whilst every throw from the other hand is thrown underneath, so all the balls follow each other around in the shape of the edge of a boomerang. For a right hand half shower, every right hand throw is an over the top throw, so the right hand always uses outside scoop & the left hand uses inside scoop.
The rhythm for this is still the same even 'left, right, left, right...' used in the cascade. You may find yourself falling into a synchronous (both hands throw together) or lopsided throwing pattern, just throw one ball a little higher than normal, wait for it to peak & then throw the next ball to get back into an even rhythm.
Again, practise this on both sides.