Digital BW, The Print

If your file was saved in a previous grayscale setup, simply change PS's grayscale setup to your new custom dot gain 
grayscale space without the file open, then open the file and let it convert, print, don't save. If your file was in 16 bit so 
much the better, as the conversion will be less detrimental.
Personally, I don't see the point in saving master printer files in a custom grayscale space that may be irrelevant as the 
technology changes, or paper, or whatever.
Tyler