One of the disadvantages with receiving an update this way is that there is only one way to install such ROM files. And in LG’s case, that’s with the LG Mobile Support Tool. So if you’re unable to install the KitKat update using the aforementioned method, or you’d rather install the update another way, such as with the more flexible method of flashing the ROM through a custom recovery, XDA Senior Member somboons has created a guide that you may want to check out.
The process explained in the tutorial essentially allows you to create a flashable ZIP package from any Android 4.4.2 update for the LG G2, regardless of device variant, and root the ROM right after you flash it. This means you can update your device by simply flashing the ZIP package from your sd card, share it online or with someone who may not have access to the LG Mobile Support Tool, or quickly and easily wipe and refresh your device without having to be bound to a PC. And for those who would rather have some visual guidance, somboons has also created a video tutorial going through the entire process.
If you would like to find out more ,visit the original thread for more information.