"A shadow is meant to create the illusion that you woke up looking good," says Paco O'Keefe from The Modern Man Barber Shop. In reality, it should be trimmed daily using one of the lowest settings on your beard trimmer. Hairs that grow too far above the cheek line and below the adams apple can be nicked off with a razor, but don't go too crazy or the natural effect gets lost.
Stubble can be immensely irritating during intimate relations, so O'Keefe recommends resting a bit of hair conditioner on it while in the shower. There's also The Soft Goat, a new stubble softening pad. As to the difference between a slovenly shadow and the perfect stubble? There are three rules that O'Keefe tells us.
"The first is to make sure you can grow a full enough beard so that it doesn't look patchy and unhealthy. The second is to make sure you are otherwise very well kept – a good haircut, dressed nicely – or it will just look like you're lazy. The final rule is that shorter stubble works on softer features and heavier shadows for sharp, more defined faces." That last rule is nicely summed up in how John Legend sharpens his softer face up with a 5 o'clock shadow and Chris Hemsworth rounds out his chiseled face with at least 24 hours worth of growth.