To get a shiny vase, you don't need to spray paint it. Just simply use a glass paint or spray paint. You can also use a glaze to make it shinier. Get a brush and brush it on the entire vase. If you don't want to spend money for a glaze or paint, you can always just buy a metallic spray paint. The most important thing you need to keep in mind is to apply more than one layer of spray. This is because the paint may not be able to cover the whole vase with just one layer.