It's okay to use a good quality pre-mixed potting soil, but I prefer to add perlite when I do that. Depends on what you're potting it into how important that is, i.e., I usually use hanging baskets with coir liners. This gives excellent drainage, which they require, so I may or may not add perlite, basically depending on whether I have some on hand. If you use clay this would also be true, but if you use plastic it would be a good idea. (You can grow fine Nematanthus in any of them.) It's starting to tempt us here with periods of spring, so I've been potting, but farther north I would probably wait. Depends a bit on what it's growing in. It helps me to remember that in nature they grow in the crotches of trees with whatever leaf litters and other detritus blows in, so they need a very loose mix in a relatively-small container.

Forgot pruning. Never hurts to do a little tip-pruning as it seems to need it when you repot, but it's really only necessary if there are long bare stems with tufts of leaves at the ends. Of course if there are buds you wouldn't want to prune them off, but everywhere you prune will, at least in theory, cause two branches to grow where only one was before, thus creating more branches to carry more flowers. Is that clear as mud?

You can prune off small cuttings, and plant them in the pot around the mother plant. They root easily in the soil and will help in making a dense compact plant, which looks best. A good way to start a new pot is to pot up many cuttings together, rather than one cutting.

I would mix your cheap store bought stuff with perlite, at about 2-1, more or less. I use the recommended type peat/perlite/vermiculite mix as I don't like the packaged stuff, made mostly of composted wood. It just seems to make for more problems down the road. But, most others seem to do fine with it.

Jon

Never buy the cheap stuff!! You get the rotten wood, cloud of gnats and poor growing. Only good for top dressing your outside plants for mulch.

AV mixtures are OK - Scott, Miracle Grow. Even better to put some extra perlite to make it even more loose. Anything to make it more breathable.

Nematanthus is OK with drought - and even flood - if the soil is breathable. The leaves are pretty and shiny even when it is not blooming. It likes sun and blooms when it is potbound - so just be patient.

The cuttings root easily in a soil - so I will go with Jon - and even start a new pot with bunch of short cuttings with 2 nodes - lower node - leaves removed goes down into soil. New pot becomes much more attractive than an old one pruned.

Love them

Irina