Here is an idea for you...
Don't go into the gents together, one of you go in and then the other goes in about five seconds later. You stand next to each other at a urinal and say "Hiya mate, how are you?", "I'm fine thank, how are you?", "I'm well thank you... nice day isn't it?", "It is a nice day".
When one of you has finished urinating and has washed their hands the other can just say "Bye mate, see you soon" and the other one of you can say "Yes, bye".
Do this at every toilet you desense in and take turns at who goes in first. Men won't know you hadn't been with each other outside so will think you have just met up. To make this easier, don't stand together to close to the toilet building, stand a short distance away where men are less likely to of seen you.
You can change the conversation and end it with "Fancy going for a drink mate" or "Do you want to go up town with me" instead of "Bye" so that you won't feel any need to worry when you walk out of the gents together.