Source as a fluid doesn't show up in either JEI or REI. How am I supposed to drag it into the export bus?

You're supposed to right-click with a Source Jar. The tooltip you would have gotten when hovering with the jar should have told you this.

Thanks, I missed the tooltip when trying to set the filter, It might be useful to say something about it in the guide book so people like me don't miss it. :)

Use a Source Jar. The rest should be self-explanatory.

For some reason that won't work for me, I have this set up (to test) and have set the filter as a source jar, what did I do wrong? (This is in the ATM Volcano Block Modpack btw)