That's about how easy it is to propagate. A couple of months ago I started off with one nasturtium 'Margaret Long' that I purchased from Annie's Annuals & Perennials in Richmond (I go to the nursery in person for the swoon factor) and now I have five baby plants, nicely rooted and one mama plant with the misshapen botanical equivalent of stretch marks. Wouldn't you sag like that if you'd given birth to quintuplets?
I did an online search first to see if the plant was under patent and could find nothing. 'Margaret Long' first appeared in an Irish garden as a sport of the double red nasturtium 'Hermine Grashof' back in the '70's, so the 20 year patent limit has come and gone. Neither of these nasturtiums set seed, so cuttings it is. I could not rationalize spending over sixty dollars for six easy-to-root plants. So Annie (who rocks the gardening world, by the way) got my first wad of dough and I am high on 'Margaret.'
My experience has been if you want to propagate nasturtiums from cuttings, just stick them into wet potting soil and you'll have roots enough to plant out in about two to three weeks.