Add new bones to a mesh that is already full rigged and keep the previous ones without conflicting?

Hi everyone,
Here is my problem : I rigged a character that has a long coat (with Rigify generated rig). The coat is rigged with him to follow the arms and legs. Now i want to add some more bones at the lower part of the coat, influencing only it (to animate it move at the wind etc), without getting off the influence of the global character rig.
I just need these new added bones on it without changing the rest of the coat’s weight.

Problem : It works well globally but when i try to move the character, the coat movement is double, because it is influenced by the general character’s rig, AND the new bones of the coat. Could i get this setup working without the coat double moving like this, that make animation impossible?
(This double weight influence problem happen in Pose mode only idk why)

Here is a video illustrating it : https://drive.google.com/file/d/1C4j-I16ZtZBPh1F-FwZteWYOkAqMBK9n/view

I precise the rig is Rigify generated, so i don’t think i can add bones directly to it without starting from scratch again, so a solution to make it work as it is in the video by fixing the problem happening at 0:09 and 0:51 would be great!
thanks by advance

You can add bones to a Rigify rig-- you just can’t regenerate the rig afterwards if you do.

Your best bet is to use a single armature, which means adjusting the existing weights as well. (It’s not as hard as you think though, give it a shot. Locking VGs and using “normalize all” operation is your friend.) Trying to do double armature deforms is kind of advanced work, and almost never the right way to do things.

But there are other things you could do here too. For example, it’s not too hard to get a couple of warp modifiers going after an armature.

Hi, thanks for your answer, i’m checking out these options soon!

You can add bones to a Rigify rig-- you just can’t regenerate the rig afterwards if you do.

Does it mean i can add bones to the already generated rig present in the video ?

You can add bones to the generated rig created with the Rigify addon. I didn’t watch your video.