y'all realize there was a point in time a 'Technique', to let in, was used twice on every exterior wall right????
Router, Radial Arm Saw, Dado blades. Framing or building cabinets??? I Do both .....
Gang the studs. Set saw to 1 5/8". Mark cut lines for the 2x4, using a 2x4. Make 1/4"-3/8" passes, in between the lines. Blast the kerf cuts out with a hammer. Use a chisel or your claw of hammer to quickly clean out the high spots. Check it with a piece of 2x4. LOL Can be done faster than getting a router out of the truck and setting it up. Will look just as good and even better covered with rock
Now if you want perfection set saw to 1.5", make very close passes. And clean out with a chisel, if needed. Will be just as effective as a dado and router.