Hi MLI,
Based on your questions my first suggestion would be to find a pilot who is experienced at that sort of thing and fly with them. It will be much more enjoyable.
Get the longest range fuel tanks you reasonably can. Eliminating stops will save time, stress and money.
Use a handling company to do the landing and over flight permits, local handling and local fuelling. This will not be cheap but with detailed oversight should lead to a successful trip.
Don’t expect a fuel stop to take less than 45 minutes. Don’t plan on flying maximum hours per day as there will be many delays. Flight plan conservatively as the day of your trip you may have any number of delays and significant headwinds.
What type are you flying?
I have crossed international borders many 100’s of times and have flown helicopters in 47 countries including throughout Africa and Europe. I do contract work like this and would be happy to help. Website for more information available on request.
Most important is to enjoy the trip!