Nate i saw where you said you clean up old seat belts. To save re-inventing the wheel and time, what have you used. I was thinking an old bucket of soapy water and a scrub brush. Like Mom used to make us do with muddy sneakers.
Seat Belt Service Pretty close ! for safety's sake , you mustn't use harsh soaps , use Woolite or anything else SWMBO uses to wash her nylons in . A soft brush helps too . Remove the entire belt from the vehicle , taking care with the delicate thin nylon shoulder washers fitted to the shoulder bolts that attach them , then pull all the way out of the retractor & clip against retracting with a clothes pin etc. , then carry into the washroom sink (I use the kitchen sink) & run warm water over the fabric whilst you gently knead it with your fingers , the sweat & accumulated dust will float to the surface & rinse off then you can begin gently scrubbing with the soft bristle brush , if they're really grotty you can make a bath of the soap and water & dunk them in and out as you work the brush or your hands , be aware that the nice white date & specification labels are going to more or less dissolve . Once the fabric is clean and has no more grit nor stiff spots , you can begin rinsing and rubbing the deep soap residue out with your fingers or the soft brush under running water , keep at this until it's absolutely clean as the soap or dirt residue you miss , will make the finished belt stiff . Hang by the retractor or buckle in a shady place for a few days before allowing to roll up or re installing , I like to remove the retractor's spring cover and gently clean out the dust , lint , mouse poop , cigarette ashes and other fun stuff before polishing the metal parts to zero rust then *lightly* lubricating with silicone . When you're finished it'll not only look nice (apart from some frayed edges) and won't have those ugly stains & creases . This isn't a quick job , it takes patience & diligence , a good way to learn both is to just sit down and do these boring a$$ but important jobs . I'm still looking for green '67 ~ '72 seat belts , especially the center one as it's gone missing and I don't like third passengers to ride sans seat belts as they tend to fly around in collisions and kill the other people in the cab..... SAFETY KNOWS NO SEASON .