I did it in a day last year, albeit, it was a day with a relentless headwind, about 0 degrees and snowing in parts, so I used the road a bit to short cut some sections. Started out nicely, but I was being battered with hail/snow showers at regular intervals in the second half. A nice big day out with good scenery but no real interest in the riding – lots of firetrack etc. No doubt I’d have enjoyed it more in better conditions and with the usual prevailing south westerly.
I have the GPS plots below if they might be of interest, although I used a lot of road in the second half (I was cold, wet and thought I was running late for my train home, although ended up being rather early). The first half is fairly accurate to the route. There is a bit of a detour off Loch Laggan too I think, due to forestry work at the time.
Bear in mind that it is not signposted, so a Garmin 800 or similar might be useful unless you want to check a map periodically.
Let me know if you want any more info.
Section 1
Section 2
Section 3
Section 4
Section 5