I personally don't use own a rotary but I have learned and come to the conclusion that you will never fully allieviate product sling. You can learn and use techniques to reduce sling but IMO, you will never stop it from happening all together.
There's a couple different ways I know how to help sling to minimum.
A.) Apply a bead of product directly from the bottle onto the paint approx. 6-8" long. Bring your rotary up to RPM setting, then with the rotary tilted ever so slightly swoop across the bead of product and once your pad completely goes over the product, lay the pad down flat and begin buffing. Meguiars Video How to remove Paint Defects explains this very well and actually shows you how to do this.
B.) Apply your product with a foam app. spread it around like a wax but do not work it in, let the rotary do this. Once your product is spread around in the area you want to buff, lay the buffing pad flat to the surface and bring your rotary up to set speed and begin buffing. I don't know how well this trick works and I don't see alot of evidence to say for sure it does work good. There's other techniques out there but I could go on and on to say what's good, but then again, everyone is different,,,,,,,AR