For a start, work with effects layers, never work directly on the image itself.
In the Layer menu you can create an adjustment layer & then choose which type of effect you wish to use. Adjustment layers can always be adjusted or deleted as long as the document has not been Flattened as you would do just before printing to save computer memory & time sending to printer. You can add other types of layers too. Using layers allows you to process effects, also duplicate original image layer.
I'll see what I can come up for you as a guide. Sounds like some masking would be appropriate though not necessary.
