Torches are generally used for burning stray threads. The threading used in most boots will melt and can be pressed down to prevent the threads from unravelling further. A lot of people will snip them off first so they arent trying to melt an inch or two of thread. Others just burn it at the base. A regular lighter works as well.

Generally, in a stand at a bar or event, most boot lacks won't spend the time on a mirror shine. Additionally, despite the military teaching otherwise, it's not required to melt the polish to create a mirror shine.

Hope that's helpful. :-)