How to undress sims?

Hello, I've been trying to craft a little dlc mod to wicked whims that would expand the exhibition interactions. I've been struggling to figure out how to get my interaction with it's attached animation to have the sim either appear completely nude or remove say only their shirt. There aren't many tutorials on this subject obviously so I've decided to take the plunge of shame with the hopes of an answer. 

I originally thought the tragic clowns coding with cas part's would help but that seems to take place after the original interaction with a loot buff. I didn't include the loot code btw
</V>

<V n="appearance_modifier" t="enabled">

<U n="enabled">

<L n="appearance_modifiers">

<L>

<U>

<V n="modifier" t="set_cas_part">

<U n="set_cas_part">

<T n="cas_part">121253</T>

</U>

</V>

</U>

</L>

</L>

</U>

</V>

I want my sims to be nude during said animation and interaction similar to how wicked whims does it with undressing their sims(When they you know) soooo is that like a whitelist blacklist thing were I have to exclude certain parts of clothing and if so how do I do this and were would I put this in a mixer interaction? Any help would be great otherwise I'm gonna have to spend another day in the tuning mine and by golly Idk if I have it in me, cheers.