If you are ordering hornworms consider purchasing additional dry hornworm chow. Hornworms eat a lot and if you want to grow them larger you might need some additional chow.
Bring 4 cups to a boil and then remove from heat. You will want to mix the dry food (1/2lb) into the water and mix until smooth. Make sure you have your containers ready because this will set fast and will start to harden. 1/2lb will make 10 - 32oz containers with about 1" of food in each.