One blaze rod can smelt twelve items, burning for 120 seconds. One coal/charcoal can smelt eight items, burning for 80 seconds. Blaze rods are the best non-lava bucket source of smelting fuel in the game.
You'll need to hunt down a blaze, hope it drops a rod, and then crush that rod into powder on a crafting table if you want to acquire some. Once you've got some, there are several things you can craft with it.
Little is known of Blaze's activities following the war, but the Razgriz Squadron did not engage in further battles again and Blaze, along with the other members of Razgriz Squadron, left the Osean Air Defense Force some time after.