Rinse your potatoes in cool or cold water to wash away any dirt. Scrub them gently with a soft sponge to clean them. You may have to cut away some green or brown spots. Use a sharp knife or vegetable peeler to carefully slice away the blemishes. If you plan to season the skins, dry potatoes are much better at absorbing seasonings. Do not pierce the skins of the potatoes if you are not wrapping them. Piercing allows the moisture to escape, which will dry out the potato. This will prevent the potatoes from sticking to the grill and create a crispier skin. In a small bowl, mix cooking oil with a small amount of butter, salt, pepper, and garlic for a tasty seasoning spread. Placing your potatoes on skewers makes the grilling process easier. Place 3 to 4 potatoes on each skewer depending on size. You can also place your potatoes directly onto the grill if you prefer. Using indirect heat, place the skewered potatoes on the edge furthest from the direct heat source. Cook over the indirect heat for 30 to 40 minutes with the grill lid down. Gradually roll the potatoes toward the direct heat.

TL;DR in Chinese:
洗土豆。 准备土豆。 吸干土豆上的水。 在土豆的表皮上刷油。 把土豆串在金属签上。 将土豆放在烤架上。 烤土豆。