Actually for traditionally spit roasting a hog you may want to consider burning hardwood down to coals and shoveling these under mr piggie. Hardwood coals burn much longer and tend to impart more flavor than plain charcoal (hardwood is usually cheaper and easier to find, also). Generally a burn barrel is set up with a coarse grate of rebar punched thru at 3 or 4 inch intervals. A fire is started and hardwood pieces/logs are added to the top of the barrel. As the logs burn to coals they drop through the grate and are shovelled into the pit. Generally a separate fire is started in the pit and allowed to burn to coals, then the coals are spread out before the pig goes on. From then on coals from the burn barrel are shoveled into the pit to maintain temps. You'd be surprised how few of the coals are needed to maintain, and preventing the pit from getting too hot is often more of an issue than not having enough fuel (Too hot a pit can cause too much fat to render too quickly into the coals resulting in a possible conflagration).