So I shoot a job to to CF card then download it onto my main desk top BUT I want to work do LR edits on my desk top while I travel or am away from my desk top. What would be the best work flow for this? I would not mind working on SmartPreviews.
Look into the command File > Export as Catalog command which creates a small catalogue of the selected images / folders / collections, and ensure you select the smart previews option. Take this on the road, and afterwards use File > Import from Another Catalog to bring the laptop catalogue into your main desktop catalogue - Lr marries cleverly updates existing images.
An alternative is to take with you your main catalogue's lrcat file and some smart previews - leaving the big previews folder on the desktop. While I used to do the Import/Export method, since we got smart previews I have found this to be a better workflow as it eliminates the Import/Export steps, and because smart previews let me take far more existing images on the road. I might edit them, copy looks from them, copy metadata, send by email etc. Afterwards you simply copy the main catalogue from the laptop back to the desktop.
If you frequently switch between laptop and desktop, the balance shifts in favour of keeping the catalogue on an external drive or on a service like Dropbox.