Can you skim coat over gloss paint?

Assuming you are using a dye-based spray on stain, yes, if the gloss is already set up and scuffed! However,while spraying or applying, gloss is too wet/tacky to work with between coats! As I do at work using Acrylic Polyurethane paints onto cabinet parts, your best bet is to apply a first coat of satin, stain over that, then a final coat of satin to seal the stain! (NEVER apply gloss over an unsealed dye based stain, as the heavy material will have a tendency to pull your stain and make the color look uneven!) As soon as the satin is flashed off (10-30min, depending on paint and temp.) you can apply your gloss. This is the method we have used for decades on HIGH quality cabinets!