Skimmed over the whole article – I wish this had been available back when I was trying to piece together the basics from the documentation. There really needs to be a 2nd part, though, with some discussion of the GVariant signatures, which the author says were ‘beyond the scope of’ this article – which is true; nevertheless, understanding that syntax (and how to use it e.g. with gdbus) is an absolute requirement for using dbus properly; and as a silly amateur, I lost so much time over them.