Don't overcomplicate with too much mopping. A great deal of the pleasure of a whole pig is the cracklings -- yet you seem intent on making the skin soggy.
Brining is not the same thing as marinating. The purpose of brining, which includes lots of salt, is to keep the meat moist -- which isn't usually much of an issue with a whole pig, even a small one. I think you may mean marinating.
Marinating for flavor isn't as efficient as injecting, and has other problems with a piece as large as a whole pig. The answer is injection.
If you want rosemary -- get a LOT, soak it, and throw some on the fire occasonally. You can do the same with whole heads of garlic. You won't actually get that much smoke penetration, but your backyard will smell GREAT.
Finally, get the past hardwood lump charcoal you can afford and that's reasonably available in your area (charcoal tends to be local). The Royal Oak sold at Wal-Mart is fine, but not great compared to -- say -- Lazzeri Mesquite. Mesquite is an especially good choice for an open pit because it brings so much more taste than most other charcoals.
If you like, you can mix every twenty pound bag of charcoal with about five pounds of hardwood chunks -- preferably pecan, hickory, oak or a fruitwood like cherry, pear or a citrus. Grape cuttings are also very good. If you bury the chunks in the fire so your chunks or cuttings won't just flame up, it actually will get some smoke into the meat.
You actually could use an all hardwood fire if you like, but you'll have to start with fairly large pieces (fireplace logs at a minimum), burn them down to coals in a separate pit, and transfer them to your rotisserie's pit on an as needed basis. Obviously, it's a major pain. Worth it? If you have the space, the help, the tools and the extra pit, yes. For 92.7% of us, no.
Rethink your mop. You don't really need to mop a whole pig on a rotisserie. It won't penetrate the skin, and only interfere with the crisping process.
One thing you may not have thought of is what do with the pig once it's cooked. Cut and clean a piece of 2"x12" plank and have it standing by so you can pull the spit from the pig. Meanwhile, make sure there's a large enough space at your buffet table for the plank. When the pig is done, and the spit removed, dress the plank and pig with garnish, and move the whole shebang to the serving table. If you don't want to use a plank, fine. Just make sure you know what you're going to do, who's going to help you do it, and whether you need tools and gloves ready.
The highest hurdle in your case is obviously a tendency to over-do. Keep it simple. Don't overcomplicate. Inject, don't marinate. Enjoy yourself.
Good luck,
BDL