Don't even work on your pack marching ability. You will to go buy a pack which will costs you hundreds of dollars and if you just use an ordinary back pack with all that weight in it you will do an injury. The pack marching should be pretty piss weak seeing as you have pogues and women going through with you.

I suppose so.
Though I don't think injury is likely by walking with a bag with a few large text books in it.
But yeah, avoiding injury is number one so just running a bit and doing some weights would be the best option.
Stretch a lot, try to get flexible.

That's not 20-30kg though. He will also need to buy proper footwear.

Yeah good point...

in Australia haven't they made it sound all nice and rosy when u go to join up due to the fact we are low on numbers
and they let u in as long as they can bring you up to their fitness level

Just saying, the best thing you can do is get into reasonable shape without injuring yourself before you even begin.