For me, this is more of a roadie tip than a commuter one, because I don't like to change once I get to work. But I think more people in this forum would benefit from it than in the 41. This is way too Fred for those people to take seriously...
I'm moving, and that means I have lots of dirty laundry, and not enough clean clothes. But I also get cabin fever, and being on the bike makes me happy. So, while I'm not doing enough laundry, I'm still getting my saddle time in. On Saturday, I was down to a pair of cotton/poly pants. I went for a ride, and it started raining about an hour later. It was windy, and the rain was coming down sideways; temps ranged from 36 to 42 degrees. It sucked. Unless I was sprinting or climbing, it felt like a sheet of ice against my legs - this is with merino long johns on underneath.
So, here's what I'm doing.
(1) Go to the thrift store ( Value Village, Goodwill, Desert Industries, etc ) and buy some merino sweaters. Get the biggest size you can find, because it has more fabric to work with. But get stuff on sale - color doesn't really matter. I got three of them; two should be enough, but now I can screw up. Total cost was about $10.
(2) Cut the arms off at the seams, then cut the front and back apart, again at the seams if possible. Use a razor blade.
(3) Wrap the cloth around your leg, mark where it meets, and cut the excess away. Sew the legs together.
(4) The legs should come all the way up to your hips; it won't work as well if you try to attach tubes to a loin cloth.
(5) Use the fabric from the sleeves to make pockets. Cargo pants are handy.
Well, I'm about half way through so far, so I can't comment on the results yet. But I'm convinced it'll work, leaving me with warm, comfortable, stretchy, perfectly fitting, sweat-wicking pants. I'm also convinced they'll be ugly as sin, like something a clown would wear, which means they'll be ready to go on laundry day.
A final tip: cashmere is probably the best fabric for cycling in. The merino pants are for practice.