Patches on Friction points might just rub more and make more noise, or cause chafing. Are you wearing thermals under your pants? Extra layers can add thickness and have expected results.
Study how you walk too. I probably walk different when I’m trying to be quiet. I’m visualizing Scooby Doo sneaking around...
Also, IN before someone says your thighs are rubbing! This can be no joke. I’ve seen people use all matter of diaper rash ointment, chamois butter, or vasaline.
Now that I think of it, maybe put a lubricant externally where your clothes are rubbing and making noise? Even a scentless deodorant may work for this.
This is a really great question and I look forward to seeing more tips. Nothing worse than buying a pair of pants online and realizing how loud they are.
First thing to pin down is what you mean by nylon pants.
Here are 3 descriptions:
1) Flex nylon is soft, flexible, and quiet. My First Lite Corrugate pants are an example. Nothing to do/can't make them better.
2) Nylon pant material used for chaps, brush pants,... They are what they are, noisy. Nothing you can do to soften or make quiet. Get new pants.
3) Earlier this year I bought a pair of UA Field Ops pants that are 100% nylon. When new, the material has the same characteristics as stiff, new, unforgiving denim jeans. If your nylon pants fit this description, do this: Get a bucket and add one gallon of water with 1 cup of salt. After dissolving the salt, let the pants soak in the solution for 3 or so hours. Upon removing the pants, hang them overnight until dry, then run them through a washer cycle on cold setting. After a couple wash and wear cycles, your pants will be softer. Same works for Carhartts and new blue jeans.
Caution: Though I've never experienced a negative outcome, do at your own risk. Be prepared for salt to strip color from metal zippers, snaps...