Just can't beat Fels Naptha bars! 99 cents at Walmart. Better for environment. I can literally get any clay stain out no matter how old or how many times it's been through the dryer. Elbow grease required. I don't use a brush though. It roughs up the fabric. Sounds strange but I use a small plastic thing that's for applying spackle to walls. Just scrape it across the fabric after applying Fels Naptha. Our HS teams use the same uniforms for many years. I was able to make the white jersey we got this year for V look 5 years younger.