Stand one corn cob upright on a cutting board. Using a sharp knife, (and an abundance of caution), cut the cob lenghtwise down the middle. Then cut each half cob in half to make four equal quarters. Repeat with each cob.
In a small bowl, add olive oil, half the Mexican seasoning, half the smoked paprike, and half the garlic powder. Add salt and pepper to taste. (I suggest ¼ tsp of each but depending upon your Mexican seasoning, you might want more or less.)
Brush each corn "rib" generously with spiced olive oil (you may have some extra depending upon the size of your corn cobs). Place corn pieces on a tray.
Preheat grill to medium high heat. While grill is heating, make the elote sauce.
To make the elote sauce, mix mayo, sour cream, remaining Mexican seasoning, garlic powder, and smoked paprika, with all of the Tajin seasoning and Cotija cheese (or Parmesan) in a small bowl. Add salt and pepper to taste. (If you can't find Tajin seasoning, see note below for an alternative.)
Place oiled corn pieces cut side down on the grill. Close the lid and grill for 8-10 minutes until the edges start to char. Then flip the spears to the other cut side and grill for another 6-10 minutes wiht the lid open. Corn kernels should start to wrinkle slightly and edges will char. The ribs should start to get soft and will bend when picked up.
Once done cooking, remove from the grill and place in a single layer on a tray. Brush immediately with elote sauce. Garnish with additional Cotija or Parmesan cheese if desired. Allow to cool slightly before serving.