Prep the slow cooker. Lightly grease the crockpot or use a liner for easier cleanup.
Mix the sauce. In a bowl, combine the BBQ sauce and Italian dressing.
If using any optional add-ins, stir them in now.
Add the chicken. Place the chicken breasts in the crockpot. Pour the sauce over the top and turn each piece to coat.
Cook low and slow. Cover and cook on Low for 4 to 6 hours (preferred for tenderness) or High for 2 to 3 hours. The chicken is done when it’s easily shreddable and reaches 165°F internally.
Shred and sauce. Remove the chicken to a plate and shred with two forks.
Return the chicken to the crockpot, toss in the sauce, and let it sit for 10 to 15 minutes on Warm to soak up more flavor.
Adjust to taste. If it’s too thick, stir in a splash of water or chicken broth. If you want it sweeter or tangier, add a bit more BBQ sauce or a dash of vinegar.
Serve. Spoon onto toasted buns, over rice or mashed potatoes, into tacos, or on top of a salad. Add pickles, coleslaw, or sliced onions for crunch.