This looks like attaching crochet/lace on the coat then add beads on top of it. This might took a lot of time to accomplish, but it looks amazing though!!!
Adding rhinestones/crystals to a cocoon coat is another amazing detail to tried on your already existing coat!
This is a super easy DIY's. Take a tight jersey mini, open up the side seam, prepare two sleeves from a regular long-sleeve french terry/jersey top, then line up to the side seam of the skirt and sew them together. Super easy, I am going to look into my closet and see if I have these two items available to do this DIY. If I do, I'll show you guys later what I do.. ;)