If you want to engrave a shape, give it a Fill color and no stroke color on the paths. When you set up a stroked path to be engraved, it will do exactly that, but it will only engrave the width of the stroke. Depending on how tall it is, it will still take up to several hours to process, because the engraving happens left to right on the bed like an old dot matrix printer.
Couple of tutorials that describe what is going on here: