I should preface my response with: my workflow involves two computers, two editors, plus an external editing company. What works for me though, may not work for you and certainly won't work for everybody.
I import every image from an event/job to a master catalog on my iMac, where it's synced to a series of rotating backup disks. Once the images have all been imported, I export that job as a separate catalogue with smart previews to a portable hard disk (any storage media would work - Dropbox, usb key, etc.).
The portable hard disk goes with my laptop and I use it as a storage disk to keep the laptop's hard disk from getting cluttered. (There is a plethora of information regarding storage disks vs. scratch disks).
Once the first phase of editing is done (culling, selecting, etc.), I send the images to an external lab for colour correcting as a trimmed down LR Catalog. with Smart Previews. This saves time uploading and the editing company prefers I send only the images I want edited - it avoids confusion.
When I get the colour corrected images back, I import them back to the master catalog (using "import from another catalog") and do my final Photoshop edits from there.
The trick with all of this is to keep the different phases separate, but to keep backups of your information.
If you want to edit the same images in the same timeframe, using two machines can become very complicated (as you know). If that is the case, I would recommend storing the files you're editing in a "cloud" of some sort - whether that's Apple's proprietary cloud or, as Caleb suggested, your own server, is entirely up to you. I have tried it in the past and it does work, it just has the potential to be painfully slow.