First time post, been lurking for a while

After reading the wiki, the forum posts here and in the 2.0 alpha forum, I'm still confused on how to install 1.2.3 for testing on embedded devices.
No big problems so far with full installs and upgrades.
I tried 1.2.2 embedded to 1.2.3 upgrade using the console, but that failed, on reboot it could not find the kernel.
Then I tried the platform change trick, with same results.
The only success I had was installing from the cd, selecting the embedded kernel, upgrade to the latest snapshot, then do the platform change, but I'm not sure if this is the way to do it since the partitions are mounted as rw and if I change fstab to mount them as ro, I get dirty disk warnings on every reboot.
How do we get 1.2.3 embedded properly installed?
How do we upgrade to the latest snapshots?