Some cas cc isn't appearing in my game properly, I assume it had something to do with what clothing categories it's set to be allowed for
so I go to edit it in SimPE using this tutorial ... but it seems to be missing a property file... how do I fix this?

Are these your files or someone else's files?

If they're your files, make sure to use the Package files that appear in SavedSims when you do "import to game" in Bodyshop. If you use the Package files from the Project folder, those are only template files, and won't work ingame.

If the files are by someone else, these are likely all Project Package files.

Project package files lack several resources needed to show up and also the proper structure, so they'll not show up in your game. The only way to make these show up (if the original creator or you don't have the original files in the SavedSims folder any longer) is to remake them (find the mesh/recolor used to make the original file, extract the recolor from the Project file with SimPE, and remake in Bodyshop).

They are someone else's
They're supposed to be complete. I remember the creator saying she didn't know why it was broken before. I ended up just leaving it alone.