They use what are called "belly bands" to keep the dogs from marking. here is a link:
http://www.doggiebellybands.com/. You can also buy them at your local PetSmart or Petco, maybe even Walmart. My neighbor used these because her puppy wasnt old enough to be neutered yet. The vet she went to doesnt spay until 6 months and her like boy was already lifting his leg at 5 months so she used these and they seemed to work well.I would also get something like Nature's Choice cleaner from Petco to clean up the marking spots for the future.