Could be mealy bugs. Wipe away the 'white stuff' with a q-tip and alchol, it won't hurt the plant. And spray with a general insecticide. The link has some images and more info. Here is a link that might be useful: http://www.denverplants.com/foliage/html/Mealy.htm

Sticky stuff (also known as Honeydew) is often found on the spikes of orchids. Generally, it is a sign of a happy plant. Some people prefer to remove honeydew because they experience some molding if they are kept under very humid conditions, this is entirely at the discretion of the grower. In some cases, spider mites and other stresses can cause a plant to exude a sticky subtance from the leaves. Check thoroughly for spider mites and other critters by tapping the leaves over a piece of white paper, looking for tiny webs and even tinier bugs.

Gidday Ed, Looks like some of the bugs are scale. Either way, it looks like natureal or hand methods might not be enough. I'd water the plant with a mix of Rogor. This systemic should do the trick. Also another good thing I do, is when I repot my plants, I include some of David Gray & Co "Systemic Insecticide Granules". This systemic insecticide is granulated and is good in the mix and gives a few months protection.

Your cactus are super etiolated. The new growth is reachin for that sun;)! If this were mine I’d cut the etiolated pieces off with a clean sharp knife, and begin to acclimate the cactus to stronger sun. Not sure if you know this, but those little white fuzzies are called glochids. Protect yourself from the, because they will get stuck in your skin, clothes, and everywhere else. Glochids are VERY irritating.