Here's what I would do. First is I would have them laser engraved. Talk to the engraver to get the in's and out's of how to do this. I would think unfinished would be better and you can clean off any residue with alcohol. However I have not done this so I'm guessing. My friend has a laser engraver and she does pens and I don't think she does any finishing before hand but I can try to reach her today.
Cutting out letters for airbrushing is not that difficult but does take practice. There are several ways to get the letters. Print them out on the computer. If you don't have the skills to do the letter layout then there is a learning curve and possibly some software for that. Then you can transfer them directly to the wood using carbon paper or you can print them in reverse and then transfer the ink to the wood using lacquer thinner or Naptha or other chemicals that melt the ink. Then you lay a piece of Frisket material on top. This looks like clear shelf paper. It has a sticky back. Once it's stuck down you cut out the letters using a razor knife. That part takes practice and some skill.
So all In all it each step takes some practice and is a good thing to learn but will take some time.
Another option is to wood burn the letters and then color inside the letters with markers, colored pencils , or dyes. Again that takes practice and some skill.
All of the above is why I recommend laser engraving.