Denatured alcohol solvent, pure 100% denatured ethyl alcohol.  

We use this to clean surfaces prior to applying epoxy, paint, or varnish, and as a wipe-down between coats of epoxy, paint, or varnish.  Also good for cleaning up tools and epoxy spills.  Denatured is relatively gentle as a solvent compared to lacquer thinner or acetone, though of course use common sense in providing good ventilation whenever you use it.

Bonus tip:  Want perfect epoxy fillets?  Allow your structural epoxy fillets to gel, usually 90-120 minutes.  Dip a gloved finger in a cup of denatured alcohol, and smooth the surface of the fillets, keeping the epoxy surface wet with denatured alcohol.  You can eliminate lumps or ugly spots in minutes.