I stumped down the blocked-in conte with my fingers, stepped back for a look and immediately reached for a defibrillator. Stumping down to this depth of tone is not for the faint-hearted and is definitely not recommended for the beginner.
But for the experienced and trained artist this excessively dark tone is the express route to obtaining the full stretch of light to dark. The rule of drawing children is that they must be dispatched expeditiously.
What this means, though, is that you do not proceed at a maniacal full pelt, but that each step is thoughtfully considered before acting.