not sure how long ago you tried it out, but ansible has an ec2 inventory script bundled along with it, that you can use instead of maintaining static manifests. This script plugs into the AWS API to get you a list of instances and metadata. Along with that, comes all the goodness of tags and pattern matching, so you can do stuff like tag_Name_DB*:&tag_type_slave to select all database slaves (if you had tags called "Name" and "type" for example)
You're right about the guide being a little too long. I was trying to establish a starting point for people looking to install and set up these tools but it would be better if there was a way to just "apt-get install" this stuff.
I'll see if I can put this together in a deb and release it somehow.