Here's something I found that was posted on the egghead forum:
If it is fresh boar, you want to do a "purge" brine for 24 hours. Simply 1 c Kosher salt, 1/2 cup regular sugar, per 1 gallon of water. You need to make enough to cover, so double, triple, etc the recipe as needed. If you want to brine in a cooler to keep the space in the fridge, simply make a heavily iced water per the measurements. Purge brine for 24 hours. (and if your buddy is smart, you guys will purge brine ALL the meat! When we did the 2 of the 3 boars, we honestly used a 100+ gallon cooler, and it was packed to the lid. I used about 5 lbs of kosher salt in that purge brine) When you see the purge brine, beware. Looks like a slaughter house but worse. Completely drain the purge brine, and all the other nasties in the cooler. Please attempt the purge brine if it is frozen, but put it in the brine mixture after it is fully thawed.
After the purge, Mix 2 tablespoons pickling spice, 1 cup kosher salt, and 1/2 cup light brown sugar (packed) per gallon of water, making enough to cover. Allow to brine in the spiced mixture for 24 hours. Rinse well, and pat dry, and ready for the Egg just like a normal butt...
Cook it as low and slow as you can, and I promise, it will be the best boar you've eaten! Seriously, we did this to two boars (butchered into parts), and had a party for about 60 boar eaters/hunters. They went nuts for the food!
As a note, we reserved the loins and tenderloins, and rubbed and grilled direct. (though those parts also took part in the complete brining process) Same with the ribs...brined, but since the boar is so lean, we cooked them indirect, but not for long.
Hope this helps!