I tend to use a combination of the 'old school' mechanical methodology together with modern techniques and knowledge.  So I'm equally as familiar with points and condensers as I am with contactless electronic ignition modules and 'Hall Effect' crank position sensors feeding timing information to an ECU.  Likewise with a carb needle working together with a jet or a fuel injector flow capacity and pulse rate.  However, older technology is where my heart belongs.  So when tuning classic cars I use, dwell angle meters, continuity testers, strobes, vacuum gauges, colortune plugs, CO analysers, feeler gauges, verniers.....sounds, smells and experience.  When many of our classic cars were built, there wasn't a computer to figure out what was wrong.  Instead it was a combination of the above 'old school' tools and instruments and just like they did back in the 60's and 70's. If these old school tools and instruments are all giving me the same result and readout then they can't all be wrong.  However anyone single one of them could provide and insight into an engine which won't start or is running out of tune.