These instructions require the purchase of Compressor, which is an extra $50, but is also the only way to really tweak your export options manually. The program is mostly just a settings generator if you're not running a server farm.
Also, by default, these instructions will only work with NTSC projects. I do not know how well they will work with projects with PAL framerates or dimensions.
( Prep: setting your export presets )
( Export the vid )
Obviously, Llamaenc is an available tool and I encourage its use (especially for widescreen vids for Premieres).
I'm just presenting an alternative (although I think I'm the only Vividcon vidder working out of Final Cut Pro X at the moment)