It might get hairy if DSL is non-trivial, IIRC Doc has plans to implement meta-DSL wrapper (a la Rascal) sometime after 1.0 launch to ease the process.
[1]: https://github.com/red/red/wiki/Red---Rebol-Dialects:--Selec...
With that said, I would appreciate if you'd listed what would you like to see in "How to bake DSL with Parse" guide of some sort, that would be really helpful when the time will come for writing tutorials and documentation.