There are a variety of cleaners provided by the stencil makers I've used in the past. A quart sized bottle is about $12-$15. Like this one from Marking Methods:
https://www.markingmethods.com/store...&idcategory=10
Lately I've begun using dish washing liquids and gently rubbing between my fingers for stencil cleaning.
Some stencils have better or worse longevity depending on size of font, the material they are made and such. I've had stencils that 10 really clean marks are about it and others that go ~40-50 with. Many variables though mostly related to how deep a cut is made and current used to obtain that. The higher the setting the more current and heat that is produced in the process.