Have a chat sometime with the people at Atsko concerning their Sport-Wash. It is supposed to rinse completely, leaving no residue. I might be able to connect you with their VP. We haven't had a conversation in a couple of years, but I may still have a connection. If you become familiar with their products, you may view them differently as far as washing and waterproofing tents.
I borrowed a tent that just reeked of dog. It HAD to be washed.