My experience with air bleed carbs has been that the principles of tuning are the same, whether air bleed or spray bar adjustable. 

Now as to the concept of adjust it until it maintains a constant RPM at idle for 15-20 seconds.  Using one indicator alone doesn't work well.  I've seen engines that would hold  a very steady low idle forever, but when you checked the transition, they would immediately die.  Thats because an engine that is running lean at the low end (not a damaging condition by the way) will run very well.  It just won't have sufficient fuel left in the system when you punch the throttle for the transition, and it dies.  Use BOTH tests (idle reliability and transition) to determine the final adjustments.  The pinch test is good for rough adjustment, but its harder to judge the small RPM change you get as you get close.. 

And remember, what we need is not the low reliable idle.  What we need is a reliable smooth transition.  We can land a plane deadstick, but if the engine won't spool up when you abort an approach, you're asking for problems.

Brad