Welcome, glad to try to help.
Anything of this type can be thinned with water, but I'd test for yourself on a scrap piece, see what you think in terms of ease of application and the final gloss - a very thin layer, applied with a damp (not wet) brush, is the safest way to go but when dry the gloss will tend to diminish as it shrinks onto the surface.
I find thinned coats fine for suggestions of greasy skin or sweat, but if you're looking for something that looks more truly wet you could well find you'd need to apply more than one coat. One thicker coat is doable (Future for example is very brushable straight from the container, as are many gloss varnishes and fluid acrylic mediums) but there's the risk of getting some brushing texture if you don't work quickly and confidently, especially if it's hot and dry where you are.
Einion