Prepare the grill. Divide the asparagus spears into 4 bunches, then align each bunch in a flat row. Thread 2 pre-soaked skewers crosswise through each bunch. (The parallel skewers will make it easier to turn the asparagus during grilling.) Brush the asparagus with oil and season with kosher salt. Grill the asparagus on an oiled rack that is set 5-6 inches over glowing coals until tender, approximately 3-5 minutes per side.