Cut the 4–6 pound whole chicken into pieces, removing skin if desired; halve large breasts so pieces cook evenly, then set aside.
Pour 1 cup buttermilk into a bowl or shallow dish and add the chicken pieces, turning to coat well.
In a large zip-top bag or bowl, combine 2 cups all-purpose flour, 1 teaspoon paprika, garlic salt to taste, and black pepper to taste; seal or mix to evenly distribute seasonings.
One at a time, remove chicken from the buttermilk and shake off excess, then place into the flour mixture and shake or toss to fully coat each piece; transfer coated pieces to a foil-lined baking sheet and cover with wax paper for a few minutes until the coating becomes paste-like.
Pour enough vegetable oil into a large skillet to come partway up the sides of the chicken (for shallow frying) and heat over medium-high until hot but not smoking; use a thermometer to monitor oil temperature.
Add chicken pieces to the hot oil in a single layer without overcrowding and brown on both sides, adjusting heat as needed so the coating browns but does not burn.
Reduce heat to maintain a steady cooking temperature and continue cooking until the internal temperature of the thickest parts reaches 165°F (use a meat thermometer); wings and legs take about 15 minutes, thighs and breast halves about 20 minutes, and cook in batches as needed.
If desired, increase heat to medium-high for a few minutes at the end of cooking to crisp the coating, then remove chicken and drain on paper towels.
Keep cooked chicken warm in the oven until serving.