The font I chose here is quite 'light'. For a house sign I'd normally choose something bolder; after all, the sign is meant to be seen from a distance. But I liked the font, so the answer is to paint the letters, make them stand out more. Because the paint lies within the V grooves, it's quite protected from the weather and stays good for a long time, much more than simply painting a sign.
One the other hand, one of the problems with painting like this is that the paint wicks into the end grain within the V groove. The end of the cut wood fibres (end grain) resembles nothing less than a mass of tiny cut straws and the is paint sucked in by capillary action. At the surface, the paint in the fibres can be seen as small streaks extending from the letters. Although not seen at a distance, it doesn't look very good close up.
Here is my attempt to eliminate the problem - at the end of the day, not entirely successful. If you have another approach or method that works better, do let me know!