After several failed attempts, the method that worked for me (with a tf101, B4O serial, build 188.8.131.52) was to use the Debugfs method. I use linux so I just read through the
RootDebugfs.batand executed the commands manually. And, this is just the first (17) steps of a longer process to actually be able to load software on the device, something we take for granted on any normal computer.
All of this was so that I can use a more open firmware, Cyanogenmod for now. I've found that manufacturers tend to abandon their devices after a while or at least slow the rate of updates, which is reasonable given that such support is a fairly substantial ongoing cost for no revenue. However, when they stop they really should provide better tools to allow users to manage their devices from then on (ideally from the beginning) with the support of the community which has proven it will actively continue to develop software for the older devices.
An issue, even when using the "official" unlock tool, is that ASUS is claiming that unlocking the bootloader will void the owner's warranty. This is becoming unfortunately common, where hardware manufacturers will wash their hands of their responsibilities based on the user's software choices. It wouldn't stand in the server or desktop computer realm; installing Linux on a Dell won't mean that they can avoid their obligations to fix their own defects. Somehow when it comes to tablets, manufacturers seem to feel justified in doing so.
This is to say that from now on, I'll have to consider more carefully the openness of a piece of hardware before purchasing it. ASUS used to be much better about this with great tools for their motherboards and good support for free software on their eee pcs (my 701 is still going strong). That had lulled me into complacency to believe it would be the same when it came to their tablets, but unfortunately that's not the case.