We were boondockers also and never has a problem finding a laundry in any town - even the small ones. We didn't use the internet for finding them. We just went. When you go into town for groceries, mail or whatever, take your laundry with you and then just ask someone when you get into town. In town is a good place to meet the locals and get lots of good information on 'hidden' things to see in the area. We got two weeks' worth of laundry done in 1.5 hours and then didn't have to think about it for a long time.
We never used campground laundries - too expensive, typically don't have the big load washers and the c.g. laundries aren't kept up like in town where they have attendants constantly wiping and cleaning. We never had an issue with dirty machines like some folks like to state.