Training is just a matter of riding a lot, but not so much you burn out before leaving. Do some runs with the trailer weighted with about 50 pounds to get use to pulling it. Each one of you. (Especially important to experience the 'feel' going down steep hills. Practice braking going down hill.) Try not to carry 50 pounds on the tour. Most novice tourers way overpack. Pack light. If you find you need something you didn't bring, buy on the road. Mail stuff you don't need home.

Do an overnighter or two for camping practice and to figure out what to pack.

40 days to Vancouver is a reasonable time allowance for young dudes like yourselves as long as you don't play much along the way. Target 6 hours/day on the bike at 12 mph. You'll be there with time to spare.