As a start I used this handy script
var sepOptions = new PrintColorSeparationOptions();
var options = new PrintOptions();
options.colorSeparationOptions = sepOptions;
sepOptions.convertSpotColors = false;
sepOptions.overPrintBlack = true;
sepOptions.colorSeparationMode = PrintColorSeparationMode.COMPOSITE;
doc.print(options);
sepOptions.convertSpotColors = false;
sepOptions.overPrintBlack = false;
sepOptions.colorSeparationMode = PrintColorSeparationMode.HOSTBASEDSEPARATION;
doc.print(options);
It does a good job, but the result is split into two separate files.
Can they be merged into a single file with separation plates in color?