The whole process is much more like drawing than I expected, with the additional benefit of being able to add textures. In this case the only instrument I used other than a coarse graphite pencil was my finger - you can see my fingerprints all over it.
I also learned that it may be possible to do this process at home by substituting citric acid for dilute nitric acid, which apart from being not altogether pleasant stuff also has to be purchased in industrial quantities. Someone on the course claimed that citric acid is the principle ingredient of kettle cleaner. I shall look into this.
Disclaimer: you copy anything I have done or suggest here entirely at your own risk.