I have not done this (dont have access to my rooted chromecast now), but I think it is possible to do it manually without using a flash device.
I believe flashcast is already installed in one of the chromecast partitions, if you already had EurekaROM. There should be a way to reboot to this flashcast without using usb. Once you are in flashcast, you should be able to use adb or ssh to login, and do a manual update using flash_image binary.
I can see this being a bit risky for regular users, and there is absolutely no need for them to do that. The folks who maintain EurekaROM had done an excellent job in creating some good "almost" failsafe methods for regular users. But if you are one of those guys who just want to be doing every step manually then ...
Originally Posted by pmcdunnough
Do I have to redo my USB stick with a newer Flashcast and then manually upgrade to the newest ROM or is there something I have to do to get the Chromecast to upgrade to the latest Eureka-Rom?