In terms of route @tango42 and @squall1 covered most of it.
My suggestions are:
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Leave early. You won’t have issues with heat in December and the road doesn’t get crowded, but it’s a good way to have the road all to yourself. Having plenty of time to look for accommodation late afternoon or mid day gives you the flexibility of finding somewhere to stay.
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Buy an easy card (at any convenience store). You add value to it and an be used at any chain convenience store. It sure as hell beats having loose change all the time.
You can also check this thread for any other info: