Shuffler's Mess is a three ball
pattern established by
Idiosensory. It is basically a 53133 siteswap thrown in such a way that
it resembles Mills Mess, with the extra two "3" throws providing most of the
added complexity to an otherwise fairly normal looking 531 pattern. Before
attempting Shuffler's Mess it is important that you already be comfortable
with both the 531 and Mill Mess, and experience with the combined 531 Mills
Mess couldn't hurt either.
To begin learning Shuffler's Mess, start with two balls in your dominant hand and one ball in your non-dominant hand. Make a vertical throw from your dominant hand and then, as that ball descends, make a roughly vertical high throw along the outside of the descending ball, catching that ball with your now empty dominant hand. The high throw is the "5" throw of the 531, so you will then follow it up with the corresponding "3" and "1" throws from your non-dominant hand and dominant hand respectively, eventually catching the "5" throw under-the-arm with your non-dominant hand.
As shown, practice this on both sides. For the next step, start by performing the same throws and catches you made in step one, except before making the final under-the-arm catch of the "5" throw you are going to make a vertical under-the-arm throw from your non-dominant hand along the outside of the descending "5" ball, catching that ball in your now empty non-dominant hand. As the ball you just threw reaches its peak you are going to make a throw with your dominant hand from the non-dominant side of your body (your dominant hand will be crossed over your non-dominant arm) toward the center of your body. You will then uncross your now empty dominant hand and catch the under-the-arm vertical ball your non-dominant hand threw. The last ball will then be caught by your non-dominant hand.
Once again, practice this on both sides as shown above. Notice how the last throw is basically a shorter mirrored version of the first throw. To run the full pattern simply make another "5" throw, this time from your non-dominant hand, along the outside of the other ball and then simply repeat the same throws you already performed with your hands switched. Shuffler's Mess is not a very difficult pattern, but you may experience some unconscious interference between this trick and the normal 531, as the throw positions and subsequent catches are very similar yet still somewhat different.