I use mostly enamel paints
Over the years I've cleaned them with paraffin/kerosene; white spirit/mineral thinners; and turpentine substitute for regular cleaning.
For an extra clean I've used cellulose thinners and proprietary brush cleaner like Polyclens
I've also washed them afterwards with washing up liquid or ordinary soap
All these have worked to a greater or lesser extent, but still seem to leave a bit of paint left deep in the brush
Then several months ago I discovered Masters Brush Cleaning Soap, and it's excellent!. It cleans thoroughly and restores the shape & quality of the brush
Watch videos on YouTube to see it in use
Now I clean with white spirit for regular or routine cleaning, and Masters now & again for a better clean
I've used various brushes - sable, synthetic, average to best quality, but have now settled on Winsor & Newton Sceptre Gold 11
They are a sable - synthetic mixture, with the qualities of sable but slightly springier and more resilient, and cheaper