It takes some effort, but have you tried Fels Naptha soap?
On tough stains of an organic variety, I can put a clean rag/towel under the stained area. Dampen the stained area. Work some of the soap (it comes in bar form) onto it. Depending on the type of cloth, I will use a clean, dampened wash cloth or a brush (jeans, canvas coats) and rub. I rinse and daub often and reapply soap as needed to keep a lather going.
Sometimes it helps if I let the first application soak a while before rubbing/scrubbing.
I check the clean rag under the area being cleaned to make sure it isn't dirty and just putting the dirt back onto the garment.
I have friends who will use Fels Naptha rubbed on a dampened area as a prewash for stains. I've done this, too. The method I described above is for the toughest ones.