I often use rubber resist applied with a brush for watercolors. I used these cheapo brushes for a class and usually would have rubbed soap into them before using to extend life, but this time I didn’t. I would normally give up and throw these brushes away. I know it’s not ‘world peace’ or a ‘cure for disease’ , BUT… I read on the web that someone had success in cleaning rubber resist from brushes with Vaseline. I tried it and I am very pleased to report that it works! Just immerse the destroyed brushes in ordinary Vaseline. Leave overnight. Clean off with soap and/or , as I did with rubbing alcohol, and voila! Actually, I repeated it twice, partly because I couldn’t believe it the first time. Try it – you’ll like it! While they don’t look perfect, they are actually quite pliable and usable!