When to shift?

You don't need to break laws, you can do this in "second gear" on the freeway. If you can get at least a partial run in all gears, so much the better. You need at least one good pull starting low, going "up and over" the peak and tapering off, so that when you plot gear ratios, you can get it to "cross.' You can do this on graph paper after you get accel / RPM data. Then compute the difference in gear ratio

Here is G-tech website. These have become more and more capable in recent years

http://www.gtechpro.com/

There may be other products that do this, I don't know what they are