Specifically, I used the ImageMagick operations "-dither FloydSteinberg -monochrome" for more contrast or "-dither FloydSteinberg -remap pattern:gray50" for more fidelity to the original image.
I was surprised that the prints were better without adjusting for gamma. If I converted the image to a linear color space before the dither operation, the print came out too dark. I'm guessing that the gamma in the non-linear color space compensated for the dot gain on the printer to cancel out the effect.