Inspired by this post, I had to try out painting the interior of a glass bottle to give good reason for why I hang onto glass jars obsessively. The results: good! Check it out:
I started with a clean canning jar and a paint sample in Honolulu Blue.
I slowly poured the paint in and swirled it around until it coated the sides. Note that I did not do this step over my leather bench, despite what this photo may suggest!
Once the sides were adequately coated, I inverted the jar over a paper plate and used a wooden skewer to help tilt it so the excess paint would slide out without pooling around the entire rim: