Digital BW, The Print

I'm confused by all the advice. Simple minded.

What's your best, most straightforward workflow from .psd and .jpg color
to a b&w image (soft proof?) that can be manipulated reasonably
predictably before being filed as tiff and opened/printed via QTRgui?

I'm looking for easy answers. I'm currently fairly successful simply
previsualizing (remember that?) how color tiffs will work in b&W, but
I'd rather see the image in advance. Lazy I guess. 

I'm not looking for a monitor depiction of b&w tone-color (cold, sepia
etc), just reasonably visually accurate b&w, as with my b&w original
negs. 

Currently QTRgui does fine with scans of original B&W film...
predictable results, adjustments easily seen in my monitor before
loading to QTR.