Several thoughts on roasting pigs. When I lived in Hawaii, we did them underground in an imu, or Hawaiian oven. Often this entailed a few days, mostly for fun. Friday afternoon, the kane (men) would show up and dig a large pit. Someone usually had access to a backhoe to make this easy. We would pile wood in the pit and then layer river rocks on top of the wood. The river rocks must be solid or they will explode from the air trappen inside of them expanding. The fire would commence and beverages would be consumed. The pig was prepared by laying down a sheet of chicken wire and layering ti or banana leaves on the wire. the pig was then placed on the wire after being rubbed with salt and stuffed with pineapples and banana stalks. Once the fire died down and the rocks were hot the pig was trussed up and wrapped in burlap sacks. This was all placed on the rocks. The sand/dirt was placed back on the pig and the mound was guarded overnite by the men to prevent someone from getting a hot foot.
In the morning, the wahine (women) would show up and bring breakfast for the now ailing kane. Who knew watching a pig cook would cause a hangover. The pig would be unburried at about two or three in the afternoon. It was let to sit for about an hour and then eaten around four or five. Again we would spend the night and go home on Sunday.
Now that I live in Arizona, this whole process is a little more difficult. We have caliche soil, which is a cement like hard packed clay. I no longer have access to a backhoe, so I have started cooking pigs above ground. I am on my second low-cost home made grill and I will share what I have learned. the top of both grills are made the same way. Angle iron for side supports, expanded metal (grate) for the grill top, and rebar across the width for support. My first grill was three feet high with 1/8th steel sides. This grill was too high to get constant heat on the meat and was subsequently lowered with a sawzall. The first grill was 4' X 5' and would handle a 140# pig with room to spare. The problem was flipping the pig far out in front of your body left you will little leverage and little strength.
My grill now is a 3' X 4' grill that can handle pigs upto 100#. The grill top is built the same, all you need is a few quick welds. Hopefully, you have a friend with a welder or you can take the parts to a welding shop with some beer and maybe a little cash. I assembled mine in under 20 minutes. The grill now just stands on top of Common Masonary Units (CMU blocks). Yep, the stuff the back fence is made of . Depending on how much heat I have, the blocks can be turned to change the height of the grill. There's the low-cost grill for pig roasting. Sure you could buy a high-dollar smoker, but hey, we all can't afford $7,000 stainless steel grills.
Prepping the pig is simple. Get a big knife, Preferably not one from your wedding gifts. Use a big Buck knife or K-bar. Cut the pig open all of the way from tail to chin. I do this in the bed of my truck after washing the plastic bed liner down. You will need to break all of the ribs both at the sturnum and dislocate them from the spine. This will hopefully leave the pig relatively flat. Now rub the pig down with a rub if you choose and wrap it in chicken wire. Build some handles near the neck and by the rear of the pig. Once the pig really begins to cook, you will not be able to turn him by his arms and legs, The meat will become so tender that they will break off.
With the blocks in place and in a relatively sheltered area, start your fire. I use mostly mesquite that I collect from new subdivisions that are knocking them over to make space for more houses. Charcoal is no sin either, but it burns hotter. Let the fire burn down some and separate it into four piles to be placed under the four meaty areas of the pig. Your ready to go cooking. Place on the grill, then pig, and start to wait. The longer and slower the pig cooks, the more tender the meat is. Even if rushed, this is a six hour project; eight is good, ten is better. Flip the pig about every hour to half hour. Build a small fire next to the big one to start new coals/new wood. This will keep the flare ups to a minimum. The melting pig fat will cause flare ups, so you might have to move some of the coals to prevent the fat from landing on them. Tell the little kids that if they crank his tail, he will cook faster. The pig should be about 160F when ready. Let sit and then carve.