Bare bones BBQ:
Mopping will not enhance the meat, just increase your cook time.
Foiling will reduce cooking time if you are pressed. It will also soften your bark. Most suggest foiling around 160F give or take if you need/want to. Waiting until a higher internal temp can lead to pot roast.
If your brisket is 5lbs, it's probably a flat. In many opinions, this is tougher to cook right (never done a flat).
Per some of the above, and I will get pushback on this, use internal temperature as a guide to reaching doneness (i.e.- we don't expect a brisket to be done at 155F but start checking on the way up). It IS done when it's done. Probe tender is what you want. Try various places, especially the obvious thickest spots.
You may want to prepare some kind of liquid to enhance moisture and flavour after slicing. I believe you can find this info in the Recipes section.
Regardless, enjoy the process.