Central Air Conditioning Air Handler

What is the proper way to clean one of those used for central air conditioning air filters again?
I used one of these- central air conditioner air filters again (the ones that go under the air handler), I was cleaning my pipe of water every month. Is this the right way? What happens if I place it back a little wet?
When entrepreneurs go to the HVAC a person's house and clean the filter, that is exactly what they do. You may want to spray on a degreaser like Simple Green, or 409 while you are cleaning. When you return, it's ok to make it a little wet, as water is pouring out of it.
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