Once you have enough fat to make one or two duck legs at a time, gradually you will accumulate more as each batch you process, you will gain more duck fat that renders off the skin. Before long I have a coffee jar full that I keep in the refrigerator. It is enough to make up to 3 legs at a time.
Recently I prepared a big batch of duck legs into confit. I think I made 20 legs in total. There are a lot of recipes on the web as how to brine the duck legs. I use only salt and water and skip the spices. I found that the spices do very little to infuse into the meat as most spices is oil and not water soluble. I actually have no idea the proportion of salt to water as I never measure the quantity except by eyeball.
there are three legs in this pot of fat; in about 5 - 6 hours they would be done
I usually eat one leg when the batch is ready. I put the rest uncover in the refrigerator to cool down and then pack two in each vacuum bag and store them in the freezer.
before long I started to put in a sprig of rosemary and that make all the difference; i typically let the legs cook in about 165F for about 5-6 hours
If you overcook the legs in the fat, you would not be able to lift them out of the oil as they just disintegrate from gravity.
here is one with perfectly browned skin done under an intensely hot infra gas broiler
In the old days duck confit is stored in the fat that they are cooked in and would keep indefinitely as the fat keeps out any oxygen. It is much easier to just pack them in vacuum bag as extracting the legs from the solidified fat is quite a messy business.
here are the duck confit packed in vacuum bags ready to be store in the freezer
the meat just short of falls of the bone as I like to have some texture and firmness; and I enjoy even the bit of skin and cartilage at the joint