CMYK out-of-gamut color control

Not sure if this is the right place to ask offset printing questions, as I guess we are more focused here in inkjet RGB printing... but anyway here it goes:

I'm having some problem to convert some photos for a book, especially in regards to the clipping of the green tones (most of these photos are of forest scenes, so this is a recurring problem). I do understand that from ProPhoto RGB to CMYK there's a huge difference in color space, the CMYK being much smaller, so a lot of color clipping is expected. However, the way I usually deal with these out-of-gamut colors in soft proofing isn't quite working.

I like to select the out-of-gamut colors through the Select > Color Range command in Photoshop CS6. I then adjust saturation or lightness as needed, to bring these colors just "inside-gamut" range. I like to do this with a few distinct selections, this way I don't undersaturate larger areas (the original area selected) unecessarily. But Photoshop is not making a selection of the smaller out-of-gamut areas scattered across the image after the first selection. Since I can't select these small areas, the only way to put them inside the gamut is by adding a lot of undersaturation to the original selection (a big part of the image), something I don't want to do.

This seems like a Photoshop bug to me... but my question is not really how I can select those smaller out-of-gamut areas (although if you know that I'd love to hear), but if that is going to be problematic when printing? I am converting mostly with Relative Colorimetric intent. What is going to happen with those out-of-gamut colors in the print?

I've done several conversions for off set printing now. I use a combination of convert to profile which cover most images but as you say greens and reds can be a problem. In this situation I use the Select > Color Range as you do. For the smaller areas I make sure the fuzziness is set quite low and use the same adjustments as you saturation and lightness. For larger areas I set fuzziness higher and use the add to selection dropper. I then make small changes to saturation and lightness, I carry on back and forth until I'm with in gamut. Some images can take a while to adjust. I don't now if that helps.

On a side note, you also have to check ink limits, printers need a max saturation of between 300% and 320%

Thanks a lot Trevor. I was actually using the color range to select the out of gamut colors directly, which works well for the first time when you have larger areas out of gamut, but afterwards it just won't select the out of gamut colors, so then I started using the selection to a sampled color and, like you said, it works.

As for the ink limits, I am aware of that too. Thanks.