I looked up the Marsh Inks online and found a great series of YouTube videos that talk about this very subject. https://www.youtube.com/watch?v=9wYX0nC0k6w I've never used inks before but I now plan to.

That said, in the past I have just used artist acrylic paints I get at a craft store. It comes in every color of the rainbow including some metallics and sparkle paint. It's water soluble so I don't have to worry about fumes and it's thick enough that I don't get bleeding. I just use a small artist paint brush to slop it in and sand off the excess. I will say that it is still best to use a coat or two of shellac on the board first though. Sharp bits will limit fuzzing of the wood grain and of course closed grain hardwood (like maple) will give sharper edges on your lettering. This last point is not useful if you are mass producing signs - too costly. But I have done fancy hardwood veneers on poplar and gotten a marvelous looking finished piece.

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