i've switched from Carafa to Midnight Wheat when using for color additions, FWIW.
works better in the is application for me.
one tip - mill your dark malt first, put it aside, then run your other grains through - helps clean off the dark malt off the rollers a bit better and you won't have any residue. i personally add just before sparging, but i fly sparge, so longer contact time than BS.
also, i personally was a bit overwhelmed with the all dark munich (weyermann) dunkel I did a few years back - one judge questioned if it was a bit underattenuated since the malt character was so rich - 76-77% attenuation and it finished at 1.013 IIRC. my thought is i either need to mash even longer at the low end next time, or mix in some pils and/or munich I.