This instructional painting pattern has 9 pages of directions to guide you with many full-color step-by-step photos. You can accent these with hot-fix rhinestones, or painted dots as you can see in both product photos.
Unfortunately, I don’t have any key charms available, but I do have many different heart charms if you would like to hang those on your ornaments for accents. Here is a link to see all them: https://tolepaintingdesigns.com/decorative-painting-categories/charms-stencils/?s=heart+charm&post_type=product
(This pattern uses DecoArt Americana Multi-Surface Satin and Extreme Sheen Pearl paints.)
This technique works best on glass surfaces. You could also use plastic but you will not be able to bake it to rapidly cure the paint. I do also have heart-shaped ornaments in the product links below, but the effect will not be as vibrant on wood.