What you are aiming for is a uniform temperature throughout the brisket around 190 degrees F. Since the surface and the fat are much hotter than the center of the brisket all you need do is keep the brisket warm to let that heat continue cooking the center. This can be done in a number of ways. Competition cooks will place their brisket(s) in a cooler to hold in the heat and let this happen. You can take your wrapped brisket and secure it in a heavy towel to hold in the heat. I put my wrapped brisket back on the smoker and close down all the vents to put out the fire. The smoker will remain warm enough to continue the process but won't add too much additional heat which can cause the brisket to overcook.
Let the brisket continue in this way for 30 minutes to an hour before checking the internal temperature again. Once you reach 190 degrees your brisket is cooked and rested.