Hello theartofcin!
We thought this was an interesting idea, so one of our Product Information Specialists, Nate, reached out to Pentel to ask. They responded that they have not tested their Aquash Water Brush for compatibility with any solvents.
Because of this, he would not recommend using a solvent of any kind in these brushes, as there the possibility that solvents may bite into the plastic components and cause the pen to leak.
You might be interested in looking at Molotow empty markers for that purpose though, as they can be used with most solvents.
- your friends at Blick Art Materials