One of my favorite topics. See the link below for my trials and tribulations.
I had to really air the trailer out to get rid of the mothball smell, then came the general stink. We removed the cushions, carpet, and curtains. I used two bottles of Febreeze on the rat fur. As a result, the smell is gone, but now it smells like Febreeze (which is much better). I'm hopeful that when spring comes and I can open the windows
all day long that the smell will lessen. All this followed a scrubbing of every smooth surface with bleach and copious amounts of elbow grease.
Someone suggested I brew a pot of coffee, then pour this into a pot and boil it off. He claimed that's what they did in houses where someone had died to clear out the odor. Well, it just smelled like a musty Starbucks after that, so that didn't work well.