You can find coconut milk in Asian specialty stores and large supermarkets. If you can't find coconut milk, make your own. Follow instructions in Homemade Coconut Milk.
To ripen ice cream in a traditional-style ice-cream freezer, after churning, remove the lid and dasher and cover the top of freezer can with waxed paper or foil. Plug the hole in the lid with a small piece of cloth; replace the lid. Pack the outer freezer bucket with enough layers of ice and rock salt to cover the top of the freezer can, using 1 cup salt to every 4 cups ice. Ripen about 4 hours. (When using an ice cream freezer with an insulated can, after churning, remove dasher; replace lid. Cover the lid with ice and cover with a towel. Ripen about 4 hours)