Combine the condensed milk, butter, cocoa powder, vanilla and salt in a small saucepan. Place over medium heat and bring to a simmer, stirring constantly with a wooden spoon. Reduce the heat to medium-low and continue stirring until the mixture thickens and, when stirred, pulls away from the bottom of the pan, about 8 minutes. Remove from the heat and place the mixture in a bowl. Cover with plastic wrap and refrigerate until chilled all the way through, 2 hours.
Lightly butter your hands. Using a tablespoon or small scoop, scoop some of the truffle mixture into your hands and roll into a bite-size ball. Roll the truffle in one of the coatings and place on a plate. Continue with the remaining chocolate. Store the truffles in the refrigerator for up to a week.