Hand washing underwear

I think I'm doing something wrong I've soaked my underwear in the bathtub or in a bucket then I scrub them with dawn or non scented laundry detergent and I rinse until the water is clean and I hang dry on hangers. The panties are not coming out clean and I noticed when I put in the washing machine it comes out cleaner but sometimes I wash my underwear twice in the machine what's the correct way to remove bacteria and discharge stains from underwear