A little clarification on adjusting idle air mixture on eddy carb

hey guys, did my 2 year plug change the other day and noticed the plugs are black, definitely running rich. Im running a edelbrock thunder series avs on my 340. I know the idle air mixture hasnt been adjusted in about 6 or so years. Edelbrock says to adjust them one at a time, here is a simple step by step listing of their procedure.

1.Fully warm engine and ensure choke is fully open.
2. Air cleaner in place.
3. Set desired speed with the idle speed screw.
4. Adjust the IMS on ONE side to get the maximum possible RPM. Do not go rich beyond the maximum speed point.
5. If the above changed the idle speed more than 40 RPM, then readjust the speed.
6. Adjust the side OPPOSITE of that in Step 4 to get maximum RPM.
7. Reset the speed.
8. Carefully turn each IMS to again get the maximum idle RPM.
9. Go leaner just enough to get a 20 RPM drop in speed.
10.Reset the speed to the desired RPM.
11.This is a Lean-Best Idle Set. Setting richer than this will not improve idle quality or performance, but could tend to foul plugs.

Is it better to do it this way or just use a vacuum gauge?

If i use a vacuum gauge do i set the idle speed then hook up the vacuum gauge and turn one of the mixture screws at a time or do they both have to be turned back and forth simultaneously to find a happy medium?

Any help or guidance is appreciated