I've been going to chime in on this to suggest you start in Google maps, import that route to Basecamp, and then to your device. It is a bit of round-about, but many find Google easier to use. Now I'd suggest you look at K and I's link. His episode 10 discusses just this method. Admittedly I fast forwarded through it, but he does seem to get the job done, though it is in excruciating detail. He really spends a great deal of time analyzing errors and how to correct them. If you can tolerate the slow pace, I think this recommendation from K and I is an excellent one.