Hot blueing is a lot harder to do as you have to ramp the temperature up gradually and not too fast. Probably not the best thing to try first as a novice.
I would recommend that people not equipped with the right equipment never do hot blueing.
The chemicals are highly corrosive - and are composed mostly of sodium hydroxide. Your clothes, shoes, skin, you name it are all fair game if you splash some out of the tank. The blueing salts will be nearly 300F when at operational temperature, and HIGHLY reactive on anything they touch.
Disposal is problematic as well.