When I did my Clayton 2.5" Overland lift, I was able to get plenty of droop out of the rear axle. Are you trying to do one side at a time?
I suggest putting the Jeep on jackstands on the frame. Then, you can use your jack under the rear differential to raise/lower the rear axle as needed.
Disconnect both shocks, and the parking brake cables (as you've already done) and the diff breather tube and e-locker harness. You want that axle to be free from anything that would prevent it from lowering enough, and you certainly don't want to damage the wiring harness or breather tube. Doing both sides together, you should be able to get plenty of droop.
But just know that you'll need to have the Jeep itself pretty high up to accommodate the amount of lowering you'll need to do with the rear axle.
The front will be the same way, just without the parking brake cables (ie locker harness, breather tube, etc).