Walkhighlands gives a time of 9 - 11 hrs to do the SGS ridge. Usually my times are just under the lower number but I took 10.5 hours to do this though it was west to east which involves extra ascent of around 150m. The walkhighlands route involves a few extra miles at the east end of the ridge by using the stalkers path down to the old road which you can avoid by planning a route straight off the mountain though careful navigation would be required to avoid crags in poor conditions. The stalkers path is a good bit longer but easy going.
I used a bike to cycle from the Cluanie inn down to the start point and did it early morning when road was quiet. The cycle took about half an hour for around 7 miles nearly all downhill. (I'm no Chris Hoy
) If using a bike I would suggest only one person does the cycle as the less bikes on that road the better and I wouldn't even consider it if the road is busy. One bus and one juggernaut passed me both doing about 60 and it's not a great experience
If thumbing a lift I would suggest making up a board with your destination ie. Cluanie Inn and only one person hitching would be far better.
Going west to east has the advantage of an escape route down to the Cluanie inn from the 2nd last munro if you are running out of time or energy or water.
If you don't fancy the campsite there are lots of laybys and parking areas on that stretch of road which are free and regularly used by campervans which may be an option for you.
All the best