If the deck planks are already bonded to the rest of the hull, this blackening will be tricky at best.
Having gone through various build logs, there appears to be three main options:
1. Do nothing, plank as tight as you can get it. Especially the smaller the scale, the more out of proportion the other options may look. At 1:100 of your Bluenose may fall well within this range.
2. Bond black, thin paper to the one edge of the planks. After bonding, scrape planks and paper flush. With larger scale ships this may be a favorable solution.
3. Mark one edge of the plank with a pencil, hardness B or HB appear to give satisfactory results, although a friend of mine had issues of smearing the pencil over the deck surface when he applied the final finish.
There may be more options, but that would require some more intensive browsing on the varioys modeling fora.
Personally, I am currently building a POF Bluenose, where I installed some interior floors and panels. I used method 1 and I am rather satisfied with the results, but it is quite personal. See
https://shipsofscale.com/sosforums/threads/yq-bluenose-by-johan.8304/page-21#post-245033