I don't marinate mine but I slow cook it in a crock pot. I put bouillon cubes in hot water to dissolve them then add beef broth, onion, green peppers, salt and pepper. You can add other things to your specifications such as carrots and potatoes.Then slow cook it all day until the meat falls apart.
I just cooked one tonight with onion soup mix, beer, cream of mushroom soup, garlic, and worchestershire sauce. It is higher in sodium, but I was short on time. I browned the roast quickly and threw it in the crockpot for eight hours.