Im not really sold on brines, if you're cooking your meat properly there is no reason for any lean meat to be dry.
Adding water into the meat isn't something I really want, nor does it lead to moistness in the meat (dispite the vast amount of articles you see about Thanks Giving turkey saying otherwise).
As we all know moistness comes from intramuscular fat (triglycerides) in cuts of meat, thats why over cooked chicken (although submerged in liquid) in the slow cooker is dry.
Brining barely puts any flavour into meats apart from salt, so from a flavouring standpoint its also pretty pointless if the duck you had wasn't very palatable to begin with.
As for making meat more tender....see the first point, dont over cook it and dont buy poor quality meat (I know yours weren't store bought
@Rasputin I was just generalising for the reasons people brine).
No it doesn't...
When meat protein is cooked it can lose around 30% of it's weight as moisture evaporates or is expelled by the protein contracting and squeezing out the fluid in the cells.
Resting the meat after cooking allows the protein to relax and suck some of the moisture back in.
Brining helps prevent this, the salt in the solution is absorbed to achieve equilibrium with the brining solution through osmosis and diffusion.
This means the meat absorbs some of the extra water and retains it whilst cooking, resulting in a moister/juicier texture.
The salt also starts to dissolve proteins in the muscles structure and cells so the meat is more tender.
The salt and aromatics within the brine also season the meat from inside to out, ie. the flavourings actually pass through the cell walls into the salt/sugar/protein solution inside the cells, so you are not just seasoning the outside of the meat.
Overcooked meat is dry because the protein structure within it contracts as it is heated and expels the liquid held within the cells.
Intramuscular fat plays no part in the moistness of lean meat as it is present in such small quantities as to be insignificant.
Try Sous Vide cooking two chicken breasts at 60°c for 80 minutes, (this is long enough to pasteurise and kill pathogens in a 50mm thick breast), one breast has been brined for 6 hours in a 5% Salt solution and one hasn't.
Both breasts need to be weighed prior to cooking and after, and the post cooking weight subtracted from the pre cooked weight, this gives the amount of moisture lost, as the breasts are cooked in a sealed vacuum pouch no moisture is lost through evaporation.
The difference in moisture content between the brined and non brined breast can be up to 20%, typically it will be around 10 - 15%, with the non brined breast having lost the most moisture.