You can grill the peppers over high or medium-high heat before or after grilling other items.
FOR A CHARCOAL GRILL: Open bottom vent completely. Light large chimney starter full of charcoal briquettes (6 quarts). When top coals are partially covered with ash, pour evenly over grill. Set cooking grate in place, cover, and open lid vent completely. Heat grill until hot, about 5 minutes.
FOR A GAS GRILL: Turn all burners high; cover; and heat grill until hot, about 15 minutes. Turn all burners to medium-high.
Clean and oil cooking grate. Toss shishitos with oil and salt in bowl. Pour shishitos from bowl onto grill and spread evenly over cooking grate. Cook until peppers are charred and blistered, 1 to 2 minutes per side.
Transfer shishitos to serving platter. Drizzle with crema and sprinkle with Tajín. Serve immediately.
