Uniforms should never see the inside of a dryer. Always air dry. If you still have stains, you can keep working on them as long as you do not set them in the dryer.
Fels Naptha works great. I basically scrub using the material itself - soap up right pants leg and use to scrub left pants leg. I use lots of water when soaping up and then usually soak in kitchen sink for 1-2 hours - basically rinse in the sink but with the drain closed. That way the Fels Naptha works it way everywhere. Then wash and hand to dry.