I agree with the other reviews this is a nice but very remote route. Dont ride past a petrol station, there arent many. The worlds most expensive fuel is in Durness, but can you blame them? Dont worry about single track, there are almost no other road users (think Olivers Mount!) you can go very fast up here.
Ok i have it on good authority that their is 1 copper to cover most of this area!
The A836 is a fast sweeping road and i recommend you fill up in Lairg.
For anyone riding north on the A838 to Durness, dont stop there - carry right on around the North coast. This is a delight that, road wise, comes in sections, rather than the whole, but the scenery is spectacular.
A really fine bit of riding shortly after Durness around Loch Enboll (wide single track but quick enough).
Turn right at Kyle of Tongue (dont cross the bridge) for a another beautiful stretch (Ben Hope) around the south end of the Kyle and up into the village of Tongue.
Tongue to Bettyhill is another wide single track, but just past Bettyhill the road widens to 2 lanes and is simply a stunning blast of very fast sweepers until Armadale.