Just a few quick notes about modding your two-cell lights:
Seeing as how you have two-cell lights you'll need boost drivers. There are buck drivers, but, buck drivers are for situations where the battery voltage is higher than the forward voltage of the emitter. Boost drivers are used when the battery voltage is less than the forward voltage of the emitter. As a general rule of thumb, you do NOT want to power a boost driver without a load on it, whether its a resistor or an emitter because you will burn it out quickly by doing so. Buck drivers are much less prone to being damaged from powering them without a load. The emitter forward voltage can be found on the spec sheet from the manufacturer or from the retail seller you are buying from.
As far as how to wire up that driver, the two wires go to the LED, red to positive, etc. Take a look at the photos and at the back side photo in particular. The brass colored circle in the middle is the positive from the battery while the brass outer ring is negative. You wire these to the switch of the flashlight so that the switch cuts power to the driver. You do not want the switch to be between the driver and the emitter in any configuration that I can think of.