Before I can answer this question correctly, I need to know how you intend to roast the pig.
My way would be to rinse the pig thoroughly in a salt water brine overnight. During the day of the salt water soaking, I would dig a roasting trench that's at least 25% larger than the pig on all sides, and 12-18" deep.
On the 2nd day, I would remove the pig from the salt water brine, rinse it thoroughly, and then marinate it in a brine of tequila, lime juice, and dry rub barbeque spices. (You can thin the tequila down with water, not to less than 50/50). The liquid should fully cover the pig.
On the day of roasting, the fire should begin in the fire pit AT LEAST 1 hour before the pig is skewered on the spit. The kindling can bbe any type of charcoal briquettes, newspaper, sticks, etc. You want a hot, easily tended, renewable fire in that pit from start to finish.
Your actual roasting fire should be hardwood, such as mesquite or hickory. The less chemical additives to the roasting fire, the better. Assuming you have a rotisserie setup with a spit to run thru the pig, the spit should be assembled ahead of time, with the pig already on it and ready to roast when the fire is.
The key to a successful pig roast is to make sure the heat comes up consistently and at a consistent temperature. Adding a few briquets when needed is ok to restoke a dwindling fire, but if you're using good hardwood that's been dry aged properly, this quick fix remedy is probably not needed.
The wood fire, by the way, should NOT be directly under the pig. You want to do this with indirect cooking, with drip pans underneath to capture the juices.
You'll know when your pig is done when the outer skin is crackling, most of the fat has been rendered off into the drip pans, and an instant read thermometer reads at least 160-170 in various points. Make sure you don't touch bone with the thermometer; you'll get a false read.
When the pig is taken off the spit, cover with tin foil and allow to rest at leat 20 minutes. The internal temperature will rise, the juices will settle back in, and you'll have a feast fit for a king's court!
OR, you could just call me and I'll do it.
