I just made barbacoa in the slow cooker... It's very easy on the prep work, but takes a little more time after everything has cooked (See if I can remember the recipe for you):
Barbacoa and Pasilla Sauce
Ingredients
3-4 lbs. beef roast
2 tbsp chili powder
2 tbsp seasoned salt (ideally Chef's Secret or some other beef / rib rub)
2 tbsp paprika
2 tbsp oregano
2 tbsp garlic
2 tbsp liquid smoke
1 large onion, quartered
1 large carrot, cut in 4 pieces
1 large celery, cut in 4 pieces
1 package dried pasilla pods (look in ethnic section of grocery store, or maybe a Mexican store), rinsed and strained
Water
Directions
Mix dry spices together into a rub mixture, and set aside. Place roast on flat surface (preferably a wooden chopping board). Tenderize roast by puncturing it on both sides with either a paring knife or a grill fork. Dab liquid smoke on roast, then rub it in. Repeat on other side. Rub garlic on both sides of roast. Finally rub the dry spice mixture on both sides of roast. Don't worry if you don't use all of the spice rub; leftovers will be added to the pot. Place roast into crock pot along with veggies. Add enough water to cover roast, and add any leftover spices. Heat roast on low for 8-10 hours. When finished cooking, remove roast and chill in the refrigerator for 1/2 hour, or until cool to touch. Save the juices from the crock pot in a large sauce pan, and bring to a simmer. Add pasilla pods to sauce pan, and let simmer for half hour. When the meat is cool enough to handle, shred with your hands (roast should be falling apart, so this should be easy to do) and save in a bowl. After simmering the pasilla pods for 1/2 hour, carefully pour contents of the sauce pan into a blender and blend until smooth. Strain mixture into a large bowl, discarding the seeds and fibrous remains (you'll probably need to continuously smear the mixture around inside the sieve with a rubber spatula since the seeds and other stuff will block the sieve and make the straining process difficult). Reheat the meat, and it is ready to serve. I like making burritos by taking a large tortilla shell, adding cooked rice (or ideally Spanish rice), barbacoa beef, pasilla sauce, salsa, cilantro, cheese (parmesan, or ideally the Mexican Cotija), and sour cream.
[Edit: Forgot the oregano]