I agree with reading CGOAB journals for great references. But how they pack their stuff is many times left out. To avoid mold and mildew, have a well ventilated place to carry wet / smelly stuff that is separated from dry / clean stuff. Many people, including me use waterproof bags and you don't want to store wet things inside a waterproof bag with the rest of you stuff. I use a full mesh bag which rides on top of my BOB trailer bag. Here it can air out all day. If it is raining, I put that mesh bag inside a garbage bag to keep things from getting really wet and heavy.
Also, unless you are cycling in a third world, you can pickup stuff that you forgot along the way and worst case, order from the internet at any public library and have it shipped to a post office ahead of you on route. I did this a few times on my cross country. Just don't forget your golf clubs and cart!!