A few more tools/resources that may be of use.

Bitcoin Scripting in general: https://en.bitcoin.it/wiki/Script

One of the Omni Dev's put together this interface for payload creations and commands to use with the Omnicore client: http://builder.bitwatch.co/

And then here is gist that shows how to use the omnicore client to manually create a tx with payload: https://gist.github.com/dexX7/352670c990ebf9ea31d6346a1519eb52