I am familiar with AC sync scope. But you don't need a sync scope to parallel a generator, as two light bulbs connected between generators will do.
You don't need to sync a DC generator to get it on line together, the voltage and engine speed have to be controlled in order to load share properly. On a DC generator more so the voltage. A shunt generator you have to control the voltage in order to load share, on a compound Generator an equalizer jumper parallels the series field which makes it load share very well, because the load goes through each generators series field.
Don