Soak four wooden skewers in water for one hour.
Meanwhile, combine all ingredients except the lemon in a large bowl and toss to coat the seafood evenly. Marinate the seafood for 20 minutes.
Thread 2 scallops and 2 shrimp on each skewer.
Preheat a grill pan over medium-high heat until the rim of the pan is hot to the touch. Brush the grill generously with vegetable oil and allow it to heat for another minute.
Place the skewers in the pan and cook, turning once, about 2 minutes per side.
Squeeze the lemon juice over the skewers and serve immediately.