Hello George,
I don't know why, but I love setting up twin carbs!!
Firstly, for the mixture settings, I think the Colortune is great. As above, I always find one runs differently to the other, so setting them up on number of flats turned doesn't always do the job, so using a Colortune at least means the mixture is the same on both carbs. However, I do it by ear, then a very sensitive rpm gauge that I have: the mixture is spot on at the point the the rpm is at the highest.
The absolute best tool I've used for blancing air speed through multiple carbs is a little wind speed gauge, otherwise called an anemometer.
http://www.amazon.co.uk/439/dp/B007P...nd+speed+gauge
The problem with a vacuum gauge is they inhibit induction through the carb as you hold it there. That means that, in effect, you're slowing the air speed by just holding it there! Also, they're fiddly to use and the little ball gets sticky when hot resulting in inaccurate readings.
With the wind gauge, you can instantly get a digital reading holding the "fan" at the carb opening. Firstly, you set the throttle flap so that the airflow at idle is the same. Then, once you have tightened up the throttle linkages, not only can you re-check the air speed at idel, you can check the airspped is the same at partial throttle openings really quickly and easily by opening the throttles with one hand and using the air speed gauge with the other.
On Amazon, wind speed gauges are cheaper than Gunson carbalancers and in my opinion, much, much better.
One last thing, on an old car I would disconnect the crank case breather (if fitted) if you are using a probe up the exhaust.