There are two ways you can perform the upgrade, either with Hubitat's USB adapter or HomeSeer's. Either way you will need HomeSeer's Z-Flash software to update them. Hubitat's USB adapter actually stores all of the Z-wave information on it, so you will not need to exclude/include any of your devices.
If you choose to use Hubitat's USB adapter you will need to shutdown the hub and insert the USB adapter into a PC. I used a Windows 10 computer, so not sure if its possible with Linux/OSX. I have also linked the Windows driver you will need in order to use Hubitat's USB adapter. You will need to manually install the driver from device manager. I had to force it to install, because Windows did not detect it as the correct driver, but it does work fine.
Otherwise you can buy Homeseer's kit that includes a Z-wave/Zigbee USB adapter and you would include this device to HE and then you can update the FW.
Then run the Z-flash software and it should find the USB adapter. The Z-Flash will basically poll for each device and give you a listing of all devices and the current FW version. The Z-Flash software comes with the Leviton firmware hex files, so you will not need to download these. You can also flash all Dimmers/Switches of the same model at one time. It will take a while to flash the devices so be patient. Also I did find that two of my dimmers were not found the first time, but after I updated the rest those two showed up and I was able to successfully update them. I would use a laptop and find a central location in the house to update them.
Just to eliminate any possible issues after updating I did go through each device and exclude them from HE, reset each device to factory defaults and re-included it. Now this is probably not needed, but I did this for more of peace of mind, all the smartapps will still exist, you would just need to re-add the device.
