No reason not to use a color head when doing BW. If you use Multigrade paper its the easiest thing in the world. One of the super cool things about this LPL (or Jobo) color head is that it is stepless, which means there is almost no change in time when you apply the filters. Increase magenta for higher contrast, increase yellow for lower contrast, or use both to create a more fine tuning.

Use both separately to create a split print, use the yellow to activate the low contrast layer of your variable contrast paper, then use the magenta to activate the high contrast layer, creating a larger dinamic range on the paper the would normally be possible with just a single pass.