Miss Elizabeth, you should talk to DiarrheaSuitcase about charging lol. I think his rate is about $2 per square inch or 90 for 4-7 hours ! But not everyone has the balls to do what he and his wife do down in Costa- amazing guy. But I think its unfair to talk about your experience, and what you charge, as the thread is about packing.
I had this problem where colour was not going in, and after a while I began to hammer in the colour! I mean I leaned on the machine ! I wasn't getting any damage either, so I stepped up the pressure. don't be afraid to hurt clients! Keep getting harder until you see weeping (not blood), and then back off a bit. Use curved mags for delicate shading, but try round shaders for packing, and less needle group if you have to.

We are mostly in the habit of using a certain pressure, and going outside that feels wrong. I had a woman in with psoriases, and slightest touch she bleeds badly (ankle). So I had to build lines so gently I was hardly touching the skin- like a feather, and this was enough to build lines. She couldn't take anything like a single pass, or she'd need a transfusion. So everyone is different, and I think you need to put your shoulder into it!