Use 1 tbsp shortening to 6 ounces chocolate
Place a 2 cup heat-resistant glass measuring cup in a bowl of very warm tap water, stir constantly until completely melted and smooth - about 15-20 minutes
Add warm water as needed
Stir with a rubber spatula
Avoid humidity and steam.
Avoid wet utensils.
Constantly stir and scrape the chocolate, don't rush it.
Use solid shortening NOT butter.
Be sure to store unused chocolate in a cool, dry 65-70 degree area with medium humidity to avoid bloom (color change to grayish).