What experimental techniques should one employ during cruise flight to determine correct airspeed to fly for max range in a headwind or tailwind? Theory demonstrates that one ought to increase speed in an headwind, and decrease speed in a tailwind to achieve maximum range.  A lengthy discussion on the theoretical solution was answered, though not clearly, here.  It is unlikely that a pilot will have the Thrust Required chart on which to draw a tangent line through the x-axis intercept at the given wind speed.

What simple techniques should the pilot employ to determine the best speed to fly given specific environmental conditions (fixed headwind or tailwind)?
An old technique is "Half the Headwind, all the Tailwind".

So if you're flying into a headwind of 20kts, increase your cruise speed by 10kts. If it's a 20kt tailwind, decrease your Cruise Speed by 20kts (but only as far as BestEnduranceSpeed).