So, I used a narrow measuring cup to make some changa. I used 91% iso so its kinda evaporating slowly. I have some yellow stains on the glass and I'm pretty sure its spice. Can I just pour a little bit of warm iso and swirl it around to reclaim said spice and than just put that little bit of iso in a shot glass with the changa herb?

I've had the same yellow residue when making changa. I added a tiny bit more IPA and poured it into a smaller shot glass like cup. Worked fine.