I'm tremendously embarrassed to be here, but couldn't resist the topic. As a divorced dad, it's on me to get the pants clean, and I've been so successful many moms ask me how I do it. It may be dirt specific, as was previously suggested, but this has worked well for us. Alabama red clay stains, Shout-out or other stain spray, wait the suggested 15-20 minutes, then soaking for two days in the summer sun in a bucket of Iron Out. Finally, Oxyclean and laundry detergent in a mix strong enough that you have to run them through the cycle twice to get the suds out. The Iron Out really is they key, and it smells so bad it can make you nauseous, but it works.
That'll do it!
I'm leaving the forum now!