So since you know how to use s3pe I get to keep this brief. Get
s3oc (Sims 3 Object Cloner) if you haven't yet, load CAS parts, select what you want and click "Clone", and yes this has to be done one at a time...
These are the settings you want to have, do NOT renumber/rename internally.
https://i.imgur.com/skarniG.png
You have a new package now. Open it and delete everything except for the CASP and KEY entries.
https://i.imgur.com/zluMywL.png
You can then modify the CASP file however you'd like to, save, and put in your game. You can also merge all those into one package if you find yourself mad with power about this and have dozens,
like so. As you can tell I really don't like messing around with Dresser :pensive: