Test-Driving Linux Mint 10 "Julia" RC (part 3) fixing grub

Please read previous article Test-Driving Linux Mint 10 "Julia" RC (part 2) USB stick to get the context

Being stuck with a broken grub ; I had to read documentations to fix the situation
I started with http://grub.enbug.org/Manual where I found out that menu.lst no longer controls the menu. But grub.cfg is the new configuration filename.
After inspecting the local HD's grub.cfg - I couldn't find any link to the USB key's uuid ?!
I then inspected the USB key's grub.cfg and definitely found mention of the local HD "Helena"

First thing I tried (rebooting on each volume) was :

sudo update-grub 

But it was like "pissing in a violin", nothing changed.

Then I found http://www.systechblog.com/some-ubuntu-problem-solving-tips.html
and http://members.iinet.net/~herman546/p20/GRUB2%20Bash%20Commands.html#GRUB_USB

The solution looked a bit tortuous but I did what was instructed there : rebooted on the live CD (I made previously)
clicked on the internal HD boot volume waited to see it on the desktop then typed

mount | tail -1
sudo grub-install --root-directory=/media/xxx-xxxx-xxxx-xxxx /dev/sda

and finger crossed rebooted and it worked - there was no grub rescue error and the laptop was now rebooting Helena

The problem was now that the USB key was useless (can't boot from it anymore)
But I did the same rebooted on the Live CD
inserted the USB key waited then typed

mount | tail -1
sudo grub-install --root-directory=/media/xxx-xxxx-xxxx-xxxx /dev/sdb

and finger crossed rebooted
and it worked too - except it kept the link to mint-8 "Helena"

And that's the happy ending of this little experiment with mint-10 "Julia"
Now the next challenge for me is to manage to install Gimp 2.7 on the USB key
But before that I think I'll be back drawing for a while ... and do some work.