Wear one and bring two
shirts
pants
underwear
socks
jacket
shoes
You are set!
Not a bad rule of thumb! I always overpack. I have heard of packing, then take out half. I’m not gutsy enough for that. But the pack 2 sounds like perhaps something I could do. How about a suitcoat?
One thing that might be good is lightweight nylon/polyester stuff. Can wash out in the sink and dry by morning. (I’m looking to buy a set of nylon sports underwear and give those a try for that reason.)