In its simplest form Dry Brining is applying salt to the surface of the meat some time before cooking.
The purpose is to modify the surface proteins to allow them to denature, then gel and “lock” moisture in the meat.
The Salt draws water from the meat, the water dissolves the salt and the salty liquid is absorbed into the layers of the meat.
Some people prefer Dry Brining because they think that wet brining dilutes the flavour of the meat.
The larger or thicker the cut of meat the longer time it needs for the salt to penetrate the meat.
There is no rule for how much salt to use. I use roughly 1 teaspoon for each kilo (2lbs) of meat.
Do a simple experiment:
Using two similar steaks, place one on a small plate
Sprinkle another small plate with salt, place the other steak on top of the salt and sprinkle the top of the steak with salt
Cover both steaks with cling wrap and leave sit on the bench for an hour.
Now uncover the steaks, you will see that the surface of the salted steak has changed, the fat will appear blotchy, and the surface will be a little shiny
Cook both steaks the same, allow to rest for 5 minutes then taste test each one to see which you prefer.