To Rinse Or Not To Rinse...that Is The Question?

My confessions on coin conservation have traversed the spectrum from enlightning to horrifying. Here is one more...
A couple of days ago I stopped by my local coin shop to get my fix of cheap foreign coins for a world type collection. At my desk I can take a closer look. Working in batches of about 20 coins, I give them their first dip in acetone. Many require further attention that ranges from scrape with a putty knife to apply a half drop of Verti-Care. (You owe it to yourself to include a trial size in your next order from Wizard. It goes a lot further than I ever imagined.)
With fresh acetone, they get a second dip. The results are shown in the picture.
You can see how they might be covered with a film and contaminates from the bath, so I repeat the process until the bathing acetone passes the mirror test.

This is very interesting. My knee jerk reaction to seeing the top picture was that the coin was toned, and in a good way. Acetone doesn't remove toning, so the yellow/brown color was organic gunk? Did you need to use a brush or other implement?