Hi fam!!! Someone has shared with me a super easy way to clean your permanently dirty clear palette & brushes. They will look brand new afterwards. Use "Easy-Off", the oven spray cleaner. Leave it on your palette for about 5 minutes and wipe/scape off the "Easy-Off". I always use paint thinner to clean it thoroughly. That's when the magic happens.
For your paint brushes, follow the same steps as above. Then twist and press the brush into a little container with some "easy-off" in it and you will see all the goo coming out. I restored ALL my brushes this way. It will do an outstanding work for your split script liner brushes. All of them came back brand new with their original bristle color!!! Once done with the goo removal, remove most of the "easy-off" with a paper towel and clean your brushes in clean paint thinner and let dry.
Hope this is useful and helping you out to save many of your brushes.