While I always start with the QTR Calibration Mode print to see all the inks from 0 to 100%, after that I use individual 21-step.tif test files and QTR profiles that print just the ink I'm interested in. For example, to see the K from 0 to 100% I use a profile that in the Windows GUI is generated by simply putting the coordinates (0,0) and (100,100) in the "point list." The program draws a straight line between them. My "K-0-100.qidf" file's active parts simply have this as the bottom line of the file: CURVE_K="0;0 100;100 "".
I print a number of 21-step test strips on a single piece of paper, but one at a time. This can be done for any ink with any ink limit, or a combination of inks, as described in the qidf file.
Photoshop can invert (image>adjustments>invert) the standard 21-step test file. See http://www.paulroark.com/BW-Info/21-Step-and-inverted.zip to see the result.
I don't know whether printing the inverted 21-step test file with the individual K-0-100 type profile would get you what you're after, but it might be worth taking a look at that approach.
(I'm looking at the realities of doing this type of thing for the usual photographer who does not have a UV densitometer, and is not a coder or color expert. My closest experience to alt process is limited to silver, where I enlarged 8x10 digital internegs. Luckily it looks like with respect to carbon as the interneg's source of density, the UV and visible light densities are relatively proportionate. Ultimately, measuring the final print and linearizing to that is what I did and probably will target. It worked for silver printing -- for a while. Unfortunately, my interneg service bureau couldn't resist messing around with their profiles, which, of course, messed up my workflow.)
FWIW
Paul