There are many techniques for how to clean oil painting brushes. Here are some of them, including some non toxic methods.
Tips for cleaning oil paint brushes
Oil Painting Guide for Schools
HOW TO CLEAN OIL PAINTING BRUSHES - Susan Harrison-Tustain Artist
Solvent Free Brush Cleaning - M. Graham & Co. : M. Graham & Co.
How to Clean Oil Paint Brushes in 4 Easy Steps
How to Clean your Paint Brushes after Oil Painting: Brush Cleaning 101
Using Walnut Oil To Clean Oil Brushes
4oz Brush Cleaner, Restorer, Clean Dried Paint Brushes, Airbrushes
How to Clean your Oil Painting Brushes without Turpentine (For Cheap!) — Irish Surrealist Paintings by Leanne Rath
Cleaning Your Oil Painting Brushes - The Best Way To Preserve & Clean – Chuck Black Art
How To Clean Oil Paint Brushes After Your Painting Session
How to Clean Oil Paint Brushes
How to: clean oil paint brushes – Mont Marte Global