Take along a good rag, wipe down your chain EVERY day after your ride, apply oil, in the morning before riding wipe off any excess oil, ride, repeat. Takes you 3min in the evening and 1 min in the morning and you will get home with a chain that is the cleanest in the neighborhood. Only 1 disadvantage to this method : you need to be very disciplined, because each time you skip a day, the dirt gets harder to get off.