I'm currently refreshing my shower (cheaply, until I can afford a professional reno) but I'm left with a grotty old shell soap dish.

Like this, but 30 years of soap exposure and abrasive scrubbing.
I am hesitant to remove it as I don't want to damage any waterproofing (and making it a much more expensive project), and I'm going for an eclectic vibe so I can live with the shape.
I'd like to know if I could use an enamel spray paint? I do have some left over White Knight ReNew Tile and Laminate Primer from a previous project if that would help.