Since my entire object is small, well, I covered the entire area.
Once you have covered your small section, you will almost immediately wipe off with a clean lint free cloth. The idea here is that you wipe away the glaze on the upper regions and highest peaks while the glaze remains in the crevices, thereby creating an aged tarnished effect.
If you need to do this more than once to achieve the desired level of "aging" you can do so.
You can see the black has remained in the crevices and has darkened some of the flat surface as well. I allowed this to happen in the corners more so than any of the other flat surfaces.
I am always going to err on the side of caution, when it comes to faux finishing. I feel like less is more, but too little is pointless. You need to find a happy medium that you enjoy, but keep in mind that the mistake made most often is going overboard on the technique. It will look contrived and busy which is not at all likely to occur in reality, and that is precisely what we are trying to emulate here.