how to revert from ext3 back to ext2?

[Nomen Nescio <nobody@dizum.com>]

My /home and / partitions are ext3. I'd like to change them to
ext2. Can I do this just by umounting and remounting them that way?

Then how do I securely wipe the journals?

Can ext2 be mounted synchronously? Would this do any harm?

Thanks.