Remove the meat from the rotisserie and chop. Set aside.
Add the butter to the large pot and saute the onions and celery for 3-4 minutes over medium heat.
Add the frozen vegetables and stir for 1-2 minutes.
Add the remaining ingredients to the pot and reduce heat to low-medium.
Simmer covered for 1-2 hours, stirring occasionally. If in a hurry, place heat on medium high for 10 minutes until boiling and reduce to medium until the vegetables are done (also covered).
Add more or less of the BBQ sauce and hot sauce, to taste.
I like to use freshly ground cracked black pepper for the taste it provides.
Cooking slowly is the best way to do this soup if time allows.
You can also thicken the soup, if desired, by making a butter/flour roux and adding to it.