Combine the gin, vermouth, maraschino liqueur, and orange bitters in a chilled mixing glass or cocktail shaker. Fill the glass almost to the top with ice. Hold the glass at the base with your index finger and thumb and insert a long spoon (such as an iced tea spoon) into the glass. Grip the spoon like a pencil and stir the drink for about 10 seconds, pressing the back of the spoon against the glass as you rotate the spoon around the circumference of the glass. The idea is to stir quickly in a fluid motion that doesn't agitate the liquid or create air bubbles. Strain the drink into a chilled martini glass or coupe, garnish with the lemon twist, and serve immediately.