Cleaning Cat Spray Off Cat and Porch?

My 8 month old neutered cat just sprayed all over his own underbelly, tail, and the wooden porch in response to the presence of a tom cat! He is usually just inside and wants in, but there is no way at this point. He is smelly and you can smell it in the kitchen as the door comes into the kitchen area. He is very fiesty and it will be dangerious to try and bathe him. Any ideas?

By Colleen