Bear Cub,

This is no help to you in your current predicament, but the time to solve this question is in the months before the tour starts. Training is more than strengthening your muscles- it is also paramount to toughen your butt and sort out saddle issues so that spending hours in the saddle is routine.

One suggestion is to try to find a quality bike shop and ask them to help with your seat issues. It may be as simple as not having chosen a saddle that is wide enough (yes, they come in various widths). See if you can find a Specialized dealer...they'll have an "ass-o-meter" that you can measure the distance of your "sit-bones". This was a revelation for me- my saddle was waaaaay too narrow and switching to a wider saddle helped a ton.

I believe in lubing the butt liberally (Chamois Buttr, etc.) before and even during the ride. Wear a padded cycling short for sure...and maybe even two pairs. Get out of your dirty shorts as soon as your ride is finished and keep the butt area as clean as you can.