Rapid heat and quench can be easy or difficult depending on what a guy is working with . As a metal cools from the glowing state it goes though many colors changes before it cools right down to the final color which is typically black . A guy needs to know what is the best color to quench on because each color will give a different hardness . It isn't easy with thin metals since they cool down too fast and your going to need fast hands and really good eyes to follow the color changes .
The proper way with something like that is to use a furnace , hold them at high heat for a period of time then quickly cool them down . Except my guess is there won't be enough carbon left to get a proper heat treat for a second time