I went there a couple of years ago. I am not sure many of the routes are half day 😛 Take plenty of food.
We did the Torridon loop (documented in many magazines and the ‘Scotland Wild Trails’ book) and also a loop of Bein Dampf (sp?)
Both were excellent big days out, the descent into Torridon (Annats?) is one of the best I have ever done in the UK but getting there with enough energy was a challenge for my brother!
As for guiding I would think a good place to start is the person in that video of Steve Peat and Danny Mac riding in N. Scotland. On the other hand if you have not been before and can read a map I think you won’t feel like you are missing out with those two routes.