Yes, that is my mail.
to generate glyphs:
You go to the font view, open the Latin section on the left sidebar, right click for example "Western European", in the popup you select all glyphs you want to generate or cmd+a and hit "Generate".
The thing with the Instances:
1) I Font Info > Master: set a distinct value for the wight (next to the popup). I suggest the width of the standard vertical stem. (I take it from the "n").

2) Font Info > Instance generate a instance and specify a value for the Weight in the Interpolation section.

Then the export should work.
Hope that helps. I really need to update the documentation ...