Hang the bottom of your gymnastics rings right at your outstretched finger tips. [Assuming you've got overhead clearance*]
Position the squat rack directly under the rings
Set your J-Cups at shoulder level to start
Our resistance bands stretch perfectly between the J-Cups. Use that band as a platform for your feet or knees.
To increase the amount of assistance, either add bands or raise the level of the J-Cups.http://hammerheadfit.blogspot.com/2013/12/jumping-muscle-ups-best-progression.html
Excellent technique for scaling for garage gym folks.