Help! Set up ArduinoDue as ISP for use with avrdude

I think that the uploader is more for small production work than prototyping.
I haven't built one yet because I'm still doing 1-offs mainly to test what I can do.

The other ways shown in this thread are okay, they work for us but it's a bit of a chore pulling out all the pieces and re-remembering and re-looking-up details to rebuild what gets used rarely anyway.