The off road training is a good idea, but it really takes SEAT TIME to learn to be a good rider off road. You won't learn much in a weekend ... but do it anyway to learn good habits and technique for you to practice!
You guys are both very experienced riders and this will help to learn off road riding tricks you will need.
I used to teach older, re-entry dirt riders, helping them learn off road riding.
A few notes:
1. Vision! Look well out ahead, down the track, don't look at the ground just in front of your front tire. LOOK AHEAD!
2. Stand up! steer with your feet. 3. BREATHE! (many hold their breath in tough conditions! BREATHE!)
4. Do not put a "death grip" onto your hand grips. RELAX ... 5. Learn to look way ahead and choose good lines. Terrain reading is critical. VISION!
6. Balance. Practice very slow speed riding to improve balance. LOOK Where you want to go!
Most Americans here know that "Football" is Soccer!
Walter Colebatch knows more about Russia and Mongolia than just about any other traveler in the world. Read his reports on ADV Rider. Top expert! He also has local contacts where you may get help, parts or a place to stay. You may be able to send tires ahead to one of Walter's contacts in Russia or Mongolia, have them waiting for you when you arrive.
The KTM 950SE was a great bike but had it's share of problems. It has Carbs, get very poor fuel economy and the engine is not nearly as strong or reliable as YOUR bikes. But the 950 is a joy to ride off road. Handles like a light 650cc enduro!
Would I pick one for your trip? NOPE! Too many break downs.