You can use whatever thinner is compatible with POR-15. It keeps moisture out of the brush and the ziplock keeps air out of there. Be careful that it is compatible with the bristle and handle material, though, or it can melt plastic eventually.

I learned that trick from a friend who is a high end house painter, and I use it when I'm doing projects that require a paint brush or roller. I keep my latex paint rollers individually in big zip locks until I am done using that type of paint. It lasts for months between uses that way.

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