Trim both ends off the beans, wash them well, and pat them fully dry with a kitchen towel.
Add the beans to a mixing bowl with salt and black pepper, spray with oil, and toss or mix by hand until every bean is coated.
Light your charcoal and let it heat up to medium high before you start grilling.
Arrange the beans on the grill grate in a single layer, leaving a little space between each one so the heat reaches all sides. I use the BBQ net grill basket. It holds better and is easy to flip.
Set the grate over the charcoal and let the beans roast for about 3 minutes, until you see a light char forming on the bottom side, then flip. Keep flipping the beans every 3 minutes, repeatedly.
Once the beans have an even char on all sides, pull them off the grate and serve while hot.