At the supermarket ask the "guy" behind the meat counter for a fine grind of ground beef. You might have to give them a little bit of time but if you go to the meat counter first put in the request then finish your shopping it should be done by the time you are ready to check out.
Do not grind beef in your food processor you will have a messy paste.
If you can not get the grocery store meat department to do this get your ground beef home and begin to brown it up, add a bit of water to the beef, about 1/2 cup and begin to really break it up. By the time the water has evaporated and the beef begins to brown the beef should be in pretty fine bits.
If you have a Kitchen Aid type mixer get a meat grinder attachment for it. You can then grind your own in fine grind for the taco or a coarse grind for things like chili and sauces.
There are hand grinders that are fairly inexpensive that attach to the counter that you could use as well. Save money and grind the meat yourself.
Hope this helps out.
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try using about a cup of water when you fry your hamburger. It helps separate it and makes finer grains. Plus the restaurants mix it with the seasonings and let it simmer forever.
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lean ground beef and there is a product from pampered chef that is specifically for ground beef and sausage that really grinds it fine it is a hand held utensil that chops it up really fine
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pampered chef