Long road trips always seem a lot more intimidating than they really are. I have done many, mostly by myself. In all honesty, they just wouldn't have been the same if I had a friend along. I'm sure they would still be a gas, but just a different kind of experience. There is something really cool about just being out somewhere having to fend for yourself.
I usually buy maps beforehand & prepare to some extent as far as the route goes, but it never goes quite right anyway. I usually start my journey by just picking a spot on the map that's about as far as I want to go that day & can still make it in time to find a place to stay. Once I settle in for the night, I will make up my plan for the next day. Obviously try & travel as light as possible.
I did a great 1100 Mile / 12 Day solo trip from Glasgow, Scotland to The Orkney Islands in the Fall of 2002 that rocked. One of the best cycling experiences that I have ever had. I had my share of problems including flatting ALL my tubes one day, getting lost at the top of a mountain,running out of road & having to walk down the side of the mountain to try & find a road. 10 Mile walk into the next town - All in the pouring rain of course. But made for a absolutely great adventure. If you are interested pictures can be seen on my webshots page:
http://community.webshots.com/user/animalmuppet
I have also attached a picture of my rig as I set out on that 1100 Mile trip.Good luck in your journey & be safe out there....