Tell me please which sentence is correct.
Wipe the benches after use!
Wipe the benches after using!
I guess the following ones is correct, but too long.
Wipe the benches after you use them!
Wipe the benches after using them!
It's perfectly idiomatic to say:
Wipe the benches after use
and this is typical of a request that you might find in a park or other public place.
It's also correct, although it takes a moment longer, to say:
Wipe the benches after you use them
Wipe the benches after using them.
This is what a parent might say to a child. It's informal and natural rather than official speak.
It's not idiomatic to say Wipe the benches after using. It leaves open the question using what?
Stick to the concise request form in your first example or the slightly longer constructions in your final examples. There's nothing wrong with taking a little longer. The question is only which one best fits the context.
The first one is correct and the simplest:
Wipe the benches after use!
You can't just say after using but only after using them, as in your last example.