The recommended amount of bleach to sanitize the tank, is 1/2 cup of bleach per 30 gallons of water. I would put the bleach in, and fill the tank up with water. If you want to make sure the bleach gets all over the inside of the tank, you can drive it around for a little while, but you won't need to go across country (or even across town) to get the bleach everywhere.
After you do this, you can just park the trailer for the night, and drain the tank in the morning, refilling it with fresh city water.
Meddle not in the affairs of dragons, for you are crunchy, and taste good with ketchup.