Digital BW, The Print

Hoping someone out there has the answer...

Without using QTR or another RIP, how do I force an Epson K3 or better printer, mine is a 3880, to print an entire image with JUST the matte black ink?
I have reason to believe this is being done but have yet to determine how.
The only thing that occurs to me at this point is to use ABW at the Warm setting and set the highlights to some lower point where LK and LLK are not brought into play.

Any ideas?