Open FullBuild2 and sort the files by Instance ID.

No in my package, like how do I find the instance of my skin ambient, etc. that I can use to search in the FullBuild?

Go through each TGI link in the CASP and the VPXYs.

The CASP TGI list links to all the files used by your clothing. In some cases it links to a VPXY or BBLN or other file type that contains links to still more files. You have to start at the CASP and follow all those links to make sure every file linked to is either in the base game packages or in your package. If it's located in an EP package you need to extract a copy, change the group ID, and put in your package. It involves a lot of tedious searching through game packages but I don't know of an easier way. I hope all that's clear!

Alternatively, look in CTU, if it can open your file - the TGIs are listed in the Textures tab. I assumed TSRW had that info somewhere too, but it doesn't seem to... maybe I'm looking in the wrong place.

Got it, thank you both