In a large bowl, which together the olive oil, both paprikas, garlic, vinegar, salt, black pepper and red pepper flakes. Add the drumsticks; turn to thoroughly coat each drumstick. Cover and refrigerate for at least 2 hours or up to overnight.
Thirty minutes before you’re ready to cook, take the drumsticks out of the fridge. Prepare a charcoal or gas grill for medium heat, making sure to clean the grates and lightly slick them with a kitchen rag or brush dipped in canola oil. Lightly brush the lemon halves with canola, sprinkle lightly with salt and set on a baking sheet.
Take the drumsticks out of the bowl, wiping off any excess marinade, and place them on the grill. Cook, turning a few times, until golden brown with some char and cooked through (an instant-read thermometer stuck into the thickest part of the meat away from the bone should read 165ºF), 25 to 30 minutes. Transfer the drumsticks to a serving platter and tent with foil to keep warm.
Place the lemons, cut sides down, on the grill and cook until charred, about 3 minutes. Transfer to the serving platter; serve immediately.