In the last year (and especially the last season) my trailer has become rather filthy. The main reason is that it was parked under a black gum tree and the leaf litter plus all the rain we’ve had made a mess on the roof.

You can see the streaks of dirt coming down the side too.

My question is: What’s the best way to wash it? I assume a car wash would be an extraordinarily BAD idea. I am thinking any kind of power wash would be damaging to the caulk and seals and cause leaks. Does this risk also apply to the water pressure in a garden hose?
Maybe a bucket and sponge is the way to go? If so, what kind of soap cleans it well doesn’t strip off the caulk?
What do you do to wash your trailer?
Thanks for ideas!