For context, I often spend a day on individual images and print them myself at large sizes. Like all of us, I try to reproduce color as accurately as possible.
I am looking for a better practical method than simply switching on soft proofing when editing camera-profiled ProPhoto files in an otherwise properly color calibrated workflow. Too often managing prints while in post to the rather blunt soft proofing out of gamut warnings results in desaturation, muted color detail and/or color shifts. Even using Photoshop's full array of color management tools, the feedback I get from the out of gamut warnings seems too crude. And I don't want to waste paper with the trial by error print and adjust method.
The best method I have found to further improve my post processing workflow may involve purchasing Chromix's ColorThink, analyzing individual files against my printer gamut as I go, and attempting to make more targeted adjustments. Before I go to that route, is that about right or is there anything better?
Couple of questions and observations. First, do you have a wide gamut monitor? Soft proofing is considerably better with one. It's useful with sRGB type monitors because there are significant numbers of colors in the monitor's sRGB gamut that can't be printed and those will show up with soft proofing. But wide gamut monitors are much better and cover the large bulk of printable colors. But not all. Particularly in the cyans.
Also, between PI and RI, only RI is colorimetric where a distinction between in gamut and out of gamut colors can be reasonably determined. PI smooshes colors near and somewhat beyond the printer's gamut so there is no distinct boundary. RI provides clear boundaries.
As for Photoshop's OOG masking. It's requires about 6 dE before it shows the mask. I have posted details of an investigation that shows that in another thread on LuLa. But under that and you won't see the mask.
The other issue is those colors that are outside the monitor's gamut. These are shown incorrectly in Photoshop because the color conversions typically increase the luminance while clipping at the gamut boundary while the printer profile, which has a different path, will not change the luminance until the printer's gamut boundary is reached. Further, printer profiles, unlike monitor profiles, typically do not significantly change the luminance beyond the gamut boundary.
One way to improve soft proofing in these situations is to desaturate the monitor's colors by 20% or so. This is a setting in Photoshop's edit->settings menu. This prevents clipping described above and improves softproofing at the cost of desaturating the entire image slightly. But it makes it easier to see problematic areas if your proof colors exceed what the monitor can show. I use this to identify and possibly edit problematic areas then switch back to normal.
There is another technique that works well with any monitor.
Make two copies of the image then convert one copy to printer space using RI, then back to your working color space also using RI. All the colors that are in the printer's gamut will be quite close, within 1 dE and typically much less, but out of gamut colors will be exactly what is printed. Now take this image and put it in a layer with the other copy of the original. Select blending subtract mode. If there are no OOG colors you will get a black image. Add in a few percent of the original layer so you can just see the original. Colors that are OOG will become immediately apparent, lightening those OOG areas in proportion to how far OOG they are.
You can also use the Info panel to read out the LAB values. I set it to floating point which provides more precision in the LAB values. Just look at the same pixels in the original and the converted image to see what the printed LAB values would be.
I also have ColorThink Pro. It's useful for exploring profile gamuts and has lots of attractive graph options but it's quite slow at processing the pixels in a large image. Most people downsample by a large factor to reduce the processing time. However, even with that I don't find the program very useful as it's hard to relate colors shown in a 3D graph to those in the image. It's sort of like looking at a histogram v an image but harder to interpret. I have not found it as useful for the kind of work you are describing compared to the two processes using Photoshop.