Synthetic base layers don't necessarily smell, I never had a significant problem with that though I almost always used machine wash. Maybe different weaves or body chemistries or hand-washing while on tour can contribute to odor, I dunno. For washcloths & towels there's the trick of microwaving while damp from wash to kill the mildew spores & bacteria, perhaps that works for synthetic base layers too? Another idea (I haven't tried it) for washing on tour is to use some powdered oxygen detergent. I bought some Nikwax BaseWash which is supposed to fight odor & improve wicking of base layers. It gets pretty good reviews though since I didn't have a significant odor/wicking problem so I don't know for sure how well it works. A little pricey but for longer tours with hand-washing it might help.