A Forum search on "ratlines" will bring up lots of discussions of this topic. I agree with GM: the Heller jigs and the one sold by MicroMark (which I believe is made by the Italian company Amati) are useless.
There are two good ways to rig ratlines on a 1/96-scale sailing ship model. One is to rig them like the originals - with very simple knots, called clove hitches. That takes quite a bit of time, but nowhere near as much as lots of people seem to think. Once you get a little practice, you can rig the ratlines on both sides of a mast in a couple of evenings.
A little vocabulary may help. The shrouds are the near-vertical ropes; they're among the thickest lines in the ship. They hold the masts in position, and transmit the pull of the sails to the hull, thereby pulling the ship through the water. The ratlines are much lighter; each of them only has to support the weight of a man. On 1/96 scale there really should be a distinct difference between the thread used for the shrouds and that used for the ratlines.
The second way to rig ratlines neatly is the "needle through the shroud" method. In this one, the fine ratline is threaded through a small, sharp needle, and the needle is shoved through the middle of each shroud in succession. A tiny bit of white glue secures the ends of each ratline, and when the glue is dry (really dry) the ends are snipped off.
In either case, it's a good idea to prepare a piece of stiff paper (file cards work well) with a series of line drawn on it the correct distance apart. (Ratlines are about a foot apart, so on 1/96 scale you need lines spaced at 1/8".) Put the card behind the shrouds to help space the ratlines.
There's a widespread impression that rigging ratlines takes some huge, mysterious skills and patience. That's a big exaggeration. It's true that there's a learning curve involved, but the curve is short and steep. I imagine the first ratline will take as much as half an hour to rig, and at that point the job will look pretty overwhelming. But the second one will take about half as long. By the time you get to the masthead you'll be rigging one ratline per minute, and wondering why people make such a big deal of rigging ratlines.
Good luck.
In either case
Youth, talent, hard work, and enthusiasm are no match for old age and treachery.