Hi, good advice already given. Sand perfectly smooth with 600-grit, feather the edges of chips, thinnest coats you can manage, gloss not matt if the film will touch it. One more thing. Many paints use solvents which could damage film/emulsion. (oh yes - and your lungs...)

So do the job away from where you keep your film, your children, your pets... and leave the camera open for at least a week before putting film in it to let solvents evaporate. The surface of the paint will feel dry in minutes but don't be tempted! It won't be fully cured for ages yet.

Haven't used grill paint myself but one Amazon reviewer claims to have painted a wood-burner a year ago and still smelling paint...

Good luck & happy holidays.