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Or alternatively, try printing a monochrome image using a colour profile created for the paper in question on your printer, and printed through the Epson driver. The usual advice is not to do this because it uses too much of the colour inks, but on the few occasions that I've tried it I've got remarkably neutral prints.>
This has been my experience as well.
One can look at existing neutral curve profiles to get a sense of what ink settings could be used to print neutral tones using QTR. IMO, making an ink separation test isn't a bad idea rather than depending upon settings of other existing curve profiles.
Don Bryant