I'd just like to second Josh's comment about taping the areas that rub. I used to suffer quite badly with this, especially in the shower after a run!
Decent strapping tape, or Therafix tape is the way to go. Just make sure you put it on dry skin, which isn't always possible. That said I have put tape on my back before a race and 33 sweaty hours later it was still in place and not so much as a red patch on my skin.
See you all out there,
Andy
www.ultramarathonrunning.com.au