You might try the Tamiya engraver tools, as they "scribe" by taking a very fine curl of material out of the cut, rather than brutally scratching like the "backside of a #11 blade" does.
Used very gently, they MIGHT work for deepening panel lines post-paint, but they're not cheap.
They are, however, worth every penny to me for the beautiful pre-paint scribing they're capable of delivering once you learn to use 'em.