Ours usually takes around 18 hours at 225to 250 degrees. This is for an 80 to 100 lb hog, using an offset, (a horizontal cooker with a separate firebox).
Does your barrel cooker have a firebox or are you building the fire directly under the hog? If under the hog, put the majority of the coals under the hams and shoulders. the ribs section will cook fast, even stuffed with veggies, etc.. If you are cooking directly over the heat, you will need to turn the hog from rib side to skin side for even cooking
For our offset...
We wrap it in chicken wire for easy turning halfway through, we keep it on it's back to hold in moisture and turn it end to end half way through. The meat is pretty tender when it's done and it's easier to remove from the cooker with wire on it.
When you leave the skin on the hog, dry rubs don't seem to penetrate the skin while cooking so I find it better to season the inside and add things like you suggested. I like brown sugar, apples and onions. Kielbasa would add a lot of flavor.
Also, I find that cooking the hog on it's back holds in more moisture, the skin holds it into the meat.
We cook large hogs overnight using hard woods and charcoal. Someone has to stay up and add wood/charcoal to the pit to keep the temperature up, we run in shifts. DH usually stays with it til 3am and I take over til 11 am, then I get a nap!
We cook with the hams closest to the fire, they take the longest. Halfway through cooking wrap the ears, ribs and shoulders with foil if they are getting too dark.
I guess it really depends on the pit you are using, over direct heat, the hog won't take as long as in an offset. One thing that is worth doing is let your hog sit for at least 30 minutes before pulling apart, this gives the juices time to equalize. It's really worth it!
Let us know how it turns out!
