There's some good stuff in the FAQs on driving technique and the TR modes:
The AULRO Discovery 3/4 & RRS FAQ
Also, this is a 10 year old sand driving thread that's a good read:
Sand driving in a D3, what am I doing wrong?
I don't tend to use sand mode that much. Generally low range and suitably low tyre pressure is all you need if DSC is off.
Cheers,
Scott

