The method you describe is how I save many tropical plants sold as annuals. Take cuttings for winter, plant outside for summer. Repeat in the fall. Coleus is a classic example of this. Also works well for many house plants, especially the creeping, non-woody kinds. When they look ratty, it's usually easier to start a new pot of cuttings than try to repot/rehabilitate the roots. Tradescantia zebrina (WJ) is the classic example of this. Theoretical discussions can be interesting, but not necessarily helpful across all kinds of plants. What are you propagating?

I have never tried this, but was reading about it in some textbooks on propagation my DH brought home. They say you can use the smaller feeder roots or the larger ones, cutting them between 1"-3". Put them on a couple of inches of substrate and cover with and inch or two of medium. The cuttings can be laid horizontally or vertically. If placed vertically be sure to get the polarity correct so that it's how they grew naturally ie. bottom part of root facing downward. It's also suggested to cut the bottom at an angle for roses. Concerning the planting medium, it was not specified, but referred to as "planting" medium as opposed to "rooting" medium, which I take to mean a more nutrient rich mix. I've done this often with other easy rooting plants such as those in the mint family with great success. (Too great sometimes!) : ) Let us know if you try it and your results. Most of mine aren't large enough yet, or if they are they root easily and truthfully, I don't need anymore New Dawn. : ( However, I have to transplant a huge one in March, so maybe I'll try this out. I don't think she'd miss a few roots.

I have black mission, Italian nero, celeste, brown turkey and an unknown variety of figs. I have rooted cuttings of Russian Red pomegranate.

Usually you would cut right at a joint. Let the cutting callus for a few days. Keep soil rather dry for the cutting. Beware the sap!