It depends on what type of Waterslide decal (inkjet vs laser) and type of Clear. Last waterslide decals I did were laser printed and used PPG two part CC. Even with that said, always good to test it with the clear you are going to use prior.

If planking is excessive I would recommend getting down a layer of clear, make your playfield touchups, apply waterslide decals, and clear over that. If you mess up on a playfield touchup or decal much easier to remove the fix if there is a layer of clear already down so you don't further damage the worn playfield.

Hi,

For al I have read (including VID's) if ya wanna place a decal, you have first to make sure the surface is even. In cas it is planked... you will have to clearcoat it first. For water decal it is always better to sandwich it between 2 layers of clear... Of course how you will implement it depends widely on the importance of the job you intend to do (full PF restoration, Partial resto, touch ups, etc...)

In your case, spray your 1K on the area to even it, place your water decal or sticker (the thinner the better)... Let dry and spay again. Not perfect but it will do the job

Stickers are thick, will stick out and catch extreme wear from ball travel.
On a beater machine that may be ok if it makes you happy.
Heat the surface with a hair dryer and lightly heat the sticker after it is applied while flattening it out with a art roller, your thumb in a cotton glove or daubing it with a clean rag.

Hi,
To apply anything on the PF, of course the clear has to be dry first
Sticker is ok for temporary repair but because of the thickness the ball will reap it fast...