Gemini 2 Hand Controller Firmware Update and Flash example
You should see a screen like the one on the below. It shows that the hand controller firmware is being uploaded to the hand controller micro SDcard.
When this screen above is done, it usually takes about 5 minutes are so, then the flashing screen will appear. See below.
After the Gemini hand controller has flashed it new firmware the HCFirmware directory in the main unit should be empty and the hand controller should have the new firmware loaded.

Note that catalog updates, *.quc files can also be updated the same way. Just upload them the same way you would a gemhc.bin file