Can I brine meat after cooking it? I cooked up a bunch of beef to slice into luncheon meat, and did some reading afterwards... and have decided that I want the meat to be brined, so it is more tender and moist, like the storebought stuff.

...except, I already cooked it. I now know that the brining should be done before it is cooked, and that is what really helps with moisture retention. But would I pick up any of the benefit by brining it now? Thanks!
It won't do anything useful.

Brining works on raw meat by denaturing some of the proteins inside the cells so they gel and hold tightly onto their water. It also gets tasty salt in.

Cooked meat has already had its proteins denatured by heat. Brining will not cause the meat to hold on to any new water. 

Basically all it will do is wash away some of the surface flavor into the brine.