The USB Flash drive must be formatted as exFAT. It is important to use this Mac since it will be used to identify the correct Windows drivers. It is relatively straightforward to create a bootable USB Flash drive to boot to the Windows 10 installer and open up a DOS prompt for troubleshooting.
To troubleshoot an issue with Windows 10 (especially boot-related issues), it can be handy to boot into Windows 10 not installed on a Boot Camp partition.
