Trans-Africa planning

A few years ago I was quite keen to do a trans Africa trip. I ended up doing a shorter trip through South Africa and Lesotho to get a feel for it before committing to a longer a trip. That trip ended badly with me being in an accident in Lesotho. All in all it was a good experience (lots of stories that can be told) but the result was that I had no money and less of an urgency for organising a longer trip.

Two years later (ie now), I have a partner in crime for a longer trip. We're still deciding on what this trip entails, and how far the budget extends. I'm selling my DRZ in order to get my finances in check for early next year when we'll be heading off.

We're probably taking small DS bikes, maybe Chinese bikes. The route will probably be up the east coast of Africa. Would like to get up to Egypt / Morroco / Isreal (somewhere like that). Maybe even into Asia. Although the budget might not extend.

What are the important things that I need to start thinking about?

- visas:
I have both RSA and GB passport. My gf has just RSA. Which countries do we need visas for? Would I be better off using my RSA passport or my GB passport?

- Carnet:
Which countries do we need Carnets for? I suppose if we sell a bike and buy a new one on route then this could be potentially challenging.

- Insurance:
What kind of insurance do we need for such a trip?

- What else should we be thinking about?

Any suggestions of places to visit (I guess we're more mondo enduro than LWD when it comes to budget).
Any tips on how much we need to budget? I see HUBB suggests 20USD per day in Africa. That seems quite low.

I know these are very vague questions, but I suppose I'm only getting started on my planning.

Thanks,
Jeff