Thanks for the tips Dragline and Oldgunsmith! I polished my internals according to the guide on Teslamap, and took great care to polish only a little and used a low speed. I actually think I did not polish as much as it could have used, as there was almost no noticeable difference in the trigger pull after I was done. But I'll stay away from the Dremel in the future, thank you for the heads-up!
As far as the loose trigger guard goes, nothing I polished has any interaction with the latch or the hole it locks into, so I'm sure that it was not caused by the polishing.