Only ever used Emerald Coast. And it was worth every penny. I used some apps for the cog tests and some gouge for the knowledge test. I scrubbed my app myself and ensured it was 100% airtight. Still got the fix it email for something that I "unfixed" to Delta's liking.
But, as the OP probably knows, it's just your dream job. You can take risks, or you can get as much help as possible. I'd give much thought to DWC CAP10 USAF's advice. It seems pretty airtight.