There are a lot of variables to consider when cooking meat for shredding, this is a basic overview of the process.
The main variable is to hold the meat internal temperature at 180F for a period of time to break down the collagen & connective tissue. Depending if you want 'completely' shredded, or 'partially' shredded, 'chunky', you should play with time and temperature. For shredded chicken breast, as an example, steam cook for 1:15 to 1:45, depending on how finely shredded you want it. It really takes some time initially to work out the best cooking time to get the desired results.
"USA Style BBQ Pulled Pork" - Most manufacturers in the states use Pork Shoulder, Pork Butt, combination, or whats called Pork Cushions, and lastly, Pork 'Picnics'. The shoulder is very large and has large 'fatty' areas, so only the people that cook and shred the product themselves use it, as the large fat pockets must be removed prior to shredding. The best product (highest quality) is the Picnics shredded, followed by pork butt.
Many processors add the ingredients and cook the products in a 'bag' by steam cooking for extended periods of time. The main thing is the thickness of the product, due to needing to hold the internal temperature up for extended period. Example: If you have two 4kg pieces of pork that you want to cook properly to shred and one is shaped like a basketball and the other is long and flat, then the long and flat one will be ready to shred in about half the cooking time.
Pork - add seasoning ingredients, sometimes pre-tumbled or vacuum tumbled with the added ingredients, into a bag that is sealed for steam cooking. Try and lay out the bag so that it is as flat as possible on the cooking rack. Step cook (70C 1 hr, 80C 1 hr, 90C 1hr, then hold rest of time at 95C for long time) The most important thing is that the internal temperature is held at 90C+ for over an hour (at least.)
Remove from cooker and when you open the bag, capture the juices from the bag to add back into the shredded product. Remove the product and put into SH-5 Shredder and slowly add whatever fat/moisture was left in the bag. In the USA, they usually package the product in a roll stock machine / tray sealer, where they add any COLD BBQ sauce to product (helps chill faster in the critical temperature zone), then it is chilled as fast as possible.