Ooh, a paintbrush! The editors of this page sure wish we knew anything at all about this item, which at the time of this writing (March 2016) remains unimplemented. It's in the accessory section, and appears to have three tiers like other skill-enhancing accessories, so perhaps someday it will boost a skill in a super fab way.
How to Obtain
You can't obtain it! All you can do is look at it here and on the Codex items page, wonder what it does, and wish you had one (even if you don't know what it does).
How to Use
One hopes this item will someday be useful in a paint-related way.