I have done two in my life.
1. I cooked very similar to how you describe above but I did not inject. The meat seemed very tough to me and I was not happy with the final product.
2. After watching someone on YouTube I cooked the second one just like the first but after I let it rest about an hour I sliced it up thin put it in the crock pot with a jazzed up beef broth / onion soup mix and let it simmer on low several hours. It made killer sandwiches.