Combine the seasoning salt, black pepper, garlic powder, onion powder, smoked paprika, brown sugar, and dried mustard in a large bowl or the chosen airtight container.
Whisk in the olive oil until the spices form a paste, then whisk in the water until the mixture is smooth and evenly combined.
Add up to 2 pounds of chicken to the bowl or container and stir or turn the pieces to coat thoroughly with the marinade.
Seal the container and refrigerate to marinate for up to 48 hours, turning occasionally to redistribute the marinade.
Cook the chicken using your preferred method until it reaches an internal temperature of 165°F (74°C).