Carnitas from a hunk of leftover grilled pork roast?
What's the best way to go about it? Will I actually get something approaching carnitas?
IMO, my non-ethnically-correct O, the one ingredient that may be missing is pork fat. If you can't finish, fancy up the cubes of pork with pork fat, it won't work as well.
Now grilled pork roast could be used for a number of things, that are good, and a bit more forgiving. Our favorite restaurant does a carnita burrito that is then covered with Mexican melting cheese and a tomatillo/jalapeno/cilantro sausa. It would be very good with your pork, esp if you were to 'stir fry' the pork with some mexican seasonings of your choice.
Green chili pork stew is also really good at this time of year. Take a look at the website "Homesick Texan" for pork recipes if you don't have the fat it would need to get the carnitias like crustiness.
Another thing that distinguishes good carnitas are that the meat stays moist, mostly because it really isn't exposed to the air until the final frying. (When the rest of the moisture has evaporated.)
My favorite version has the pork cooking covered in a mix of dark beer and orange juice, and then as the fat renders off the pork, it coats the meat and then finally crisps it.
So...how's your pork?
Since it's already cooked, I don't see how. It's the method of cooking that makes it what it is.