I found Scotchguard yellowed over time, especially with exposure to sunlight, but it is effective as a barrier. I used Arm & Hammer baking soda and peroxide toothpaste. A dot of that on a white slightly moistened cloth or a soft toothbrush usually took care of small stains on both fabrics.
Or, do what squared-away officers do. Buy 3-4 at a time. Always have one inspection-ready and pristine and only used for inspections. Use the others in rotation, cleaning as you go, or just have a ready replacement. The mids at USNA used to wonder how all the senior officers managed to look fairly pristine in whites all the time. A peek inside my office closet would have revealed 5 pairs of white shoes, two fresh sets of whites on hangers, and a stash of fresh combo covers.
Thanks Captain. It’s poly cotten blend. It’s for my DS who just made Chief in NJROTC. I have plenty of practice cleaning blood and clay stains out of baseball pants with oxyclean, peroxide and Fels-Naptha bar soap
Another good one for the plastic covers is Soft Scrub. My Mids cover received a good cleansing during his 3 month spring break at home. I did it half and half to accentuate the before and after. Wowzers...AND it has a disinfectant element bc of the bleach.