I did my own a couple of weeks ago now, Captive bolt two inches above the eyeline ,central . I lured her into a borrowed pig weighing scale with a bucket of nuts, then gave her a bath first to get her nice and clean while she was in the crate. pay particular attention to the legs and feet and underside , she must be nice and relaxed and eating nuts when you drop her so totally unaware of what's happening
You must have every thing prepared first , I spent a lot of time gathering all the kit together that was needed, things like planning where to do it, and rigging up the electric winch in the right position , having your very sharp knifes handy and a new clean large plastic trug for the blood if you plan to make your own black pudding, you will of coarse pre-cook the pearl barley and soak the oatmeal overnight and have you spices and backfat ready prepared with a big pan of water simmering standing by
The whole thing must be planned like a military operation. After the stun you must work quickly ,and remember you could have a hundred killo of pig on your hands so the winch is essential, winch her out of the crate and bleed her while the heart is still beating to pump the blood out, this is what kills her, the stun just does what it says on the tin. Be careful not to pierce the intestine when you first open her up or you will have a mess on your hands, also be carefull not to break the gaul bladder when removing the liver.
After gutting and shaving you can cover the carcase with an old duvet cover and let it hang for a few days to set the flesh and make butchering easier.
Good luck