There are lots of tricks. Here are couple of ideas:
As stated, let the "weaker" of the two paddlers remount first.
Have the first person straddle the boat (one leg on either side of the boat, however, for shorter paddlers, this is nearly impossible since the walls are just too tall to straddle. So in the case of a smaller paddler, both feet must remain inside the ski. In order for shorter paddlers to add stability, a sculling brace should be practiced beforehand, and used while the second person remounts.
To ease the remount of the second person, remember that you are already wet - since you are in the water. First step is to remain relaxed in the water. Second step is thinking and positioning yourself. If you are weaken, or if you have difficulties remounting, then DO NOT attempt to pull yourself out of the water. That's right: do the opposite of what you have been told: do not remount. First, take a really big breathe of air as if you wanted to free dive to 90 feet. Then, simply "raise" both arms to sink feet first. Finally, as you start floating back to the surface, kick like a bat out of hell. I assure you that with practice, this remount technique is one of the easiest - but it's all in the timing, so you must practice it a bit.
Just think of yourself as launching out of the water, and using your positive buoyancy do the work for you.
Ludovic
(Brittany, France)