I dont marinate the meat but I use neck not shoulder,if you wanted to you could use shoulder & give it a soak in red wine garlic etc. Neck has 2 lines of fat that keep it tender.
So I fry 1 chopped onion,chopped red pepper,& a full chorizo less taste test(mighty fine) in olive oil 4 min then add 2 fat cloves of garlic, 1 more minute then take everything out of pan leaving as much pan juice as I can,had some butter on hand that looked at me the wrong way so it went in too. Then fry cubed pork in the panjuices ,chorizo leaves a bit behind.When its coloured sprinkle with 1x teaspoon sweet paprika ,1x smoked paprika,1 x teaspoon cumin,good fat grind black pepper.Fry 1 min. Then good slug sherry or madeira to deglaze pan ,give it a good shake & stir .Then add stock.I had pork stock (smoked ) fresh chicken frozen pork won.The chilli that I soaked in hot water,I read packet its from Peru lovely depth of flavour not HOT. Put chorizo,onion,pepper mix back in. I decided against the canned tomatoes & used 1/2 a bottle of tomato passatta instead. Meat should be covered ,gentle simmer until meat is tender.I cut my pork big but thats just me.