A Time Apart: Fred Corrective Blendshapes Lower Body

After hours of wrangling and a dozen file variations later (no joke, I literally have 12) I have got the lower coat to behave itself and interact with the shorts as it's supposed too the best I can... There's just one bit of popping on the character's left side that I can't seem to get rid of which taunts me but I can live with it for now (below). 

There are some positions the coat won't make without a rig such as when my character sits on the ground he would be sitting on his coat which would need a more complex position.

Left leg moved forward

Right leg moved backward

Right leg forward

Left leg backward

The task of creating blendshapes for the lower body started smoothly and simply with the knee and shorts - no problems. Then it all changed when I got to the coat, my first problem started with not having enough preview keys which I needed because the coat is asymmetrical and does not mirror well and at one point I was accidentally editing the right under the left deformers - not good. Then there were moments where I had edit turned on for the wrong deformer or not at all... Also not good. Then when I did do it properly I started to get popping, lots of popping, such as when I scrub the timeline and move the joints it pops, when I delete preview animation - pop, when I click off edit it pops, as shown below. At one point I tried putting a deformer with a value of 0, 0, 0, (equal to the neutral I'm guessing) just to see if I could correct the corrective shapes... It failed and made it worse.