Unsanitary bathrooms are straight from hell. It's genuinely disgusting. It's usually the remote bathrooms in rural roads that are really gross and dirty. I'm sorry you had to experience that.
Then how do people do that without getting their clothes all soaking wet?
In squatting holes they usually have a low pressure shower bidet or a container just pouring water on it and then they scrub it with their hands. It gets your hand dirty but it gets the job done with minimum splashing.
Every description online is like very vauge and overly modest in using a bidet and I just need something explict step by step.
I'm not sure how much it helps but wikihow has a guide.
I would excommunicate all cabbage farmers and declare a papal bull declaring all poopy butts heretics.