In a large bowl, combine buttermilk and hot sauce. Add chicken thighs, ensuring they are fully submerged. Cover and refrigerate for at least 2 hours, or overnight for best results.
In another bowl, whisk together flour, smoked paprika, garlic powder, onion powder, cayenne pepper, salt, and black pepper.
Remove chicken from the buttermilk marinade and let excess drip off. Dredge each piece in the flour mixture, pressing lightly to ensure an even coating.
In a large skillet, heat about 1 inch of vegetable oil over medium-high heat until it reaches 350°F. Carefully add the chicken, cooking in batches if necessary to avoid overcrowding. Fry for 5-7 minutes per side, or until golden brown and cooked through.
Transfer the fried chicken to a paper towel-lined plate to drain excess oil.
To assemble the sandwiches, place a piece of fried chicken on the bottom half of each bun. Top with pickles and coleslaw, then add the top half of the bun.
Serve immediately and enjoy your Nashville hot chicken sandwiches!