So… I wasn’t going to post a skirt tutorial because it isn’t really necessary to re-make the skirt; the one from the official Disney costume is really nice as it is! But, I did modify mine, so I figured I’d show what I did in case anyone else wants to do it too.
For the Grub’s costume, I modified the skirt to replace the belt so that it matched the top’s fabric, and I put in a full length grass skirt.