Your posts indicate a paint finish. Don't paint it! Scrape the big chunks the housing off first, scrub it down with solvent (paint thinner) or a mild degreaser (I don't know what Evapo-Rust does) rinsing with dish soap in between steps. Don't use oven cleaner, it has an acid base and will leave an ugly white surface, in fact avoid anything with acid in it. A mild scrub brush works, steel wool or a wire brush will wreck the surface. You might try Simple Green (it has an odor that makes me sick so I don't use it) or Krud Kutter available at Home Depot in the paint department. I don't know what's available in Canada (make a run to New York if you have to).
Jim