My trailer had some leaks. My strategy was to do all the maintenance and not try to locate and eliminate every individual leak. I started at the top, and worked my way down to the step release slot.
At the top, I replaced all the clearance lights with new gaskets and butyl putty. I replaced the sewer vent seal gaskets and sealed the cap screws with Vulkem 116 gray. I replaced the air conditioner, removed the television antenna, replaced the roof vents with Fantastic fans, sealed seams, sealed the awning channel, found and fixed 5 missing rivets under the awning roller, replaced all the window and door gaskets, and sealed lowed body seams and rub rail rivets.
I now have a dry trailer. We just had a 5 inch in two hour rain and totally dry.