Well, James, it sounds as if you could use the course!

Did you see my reply to Pankaj about the two-stage process?
Think of it as a two-stage process. The first stage is purely symbolic: you select a point in the chart and imagine moving it forward (or, in the case of converse directions, backward) through the chart, passing through the terms and encountering the bodies and aspects of the planets, fixed stars, etc.
The second stage is translating this symbolic motion into natural, using the primary motion of the celestial sphere following birth (never before birth): how can these points be brought into contact? In the present case, it is only by the aspect point moving up to the eastern horizon.
So you begin by deciding on a significator: a point that signifies the matter you want to investigate. Next, you move that symbolically along until it meets a point that 'promises' some change for better a worse: a promissor.
Then you figure out how that contact will come about by the natural (clockwise, at least if you live in the northern hemisphere) motion of the celestial sphere. In direct directions, this will be by keeping the significator fixed (even if it is a planet) and letting the promissor move towards it.
Primary directions is actually a modern term: it was coined by Placidus in the 17th century (because he invented another technique which he called secondary directions, and he needed to distinguish them). Before that, they were just called directions. But yes, the primary motion used for (primary) directions is the same as that of the sun over the course of a day: the rotation of the celestial sphere, or of the earth around its axis, if you prefer.
The example you give is a primary direction, but a converse one (as I said before), where from the point of observational astronomy the promissor (Mercury) is kept fixed and the significator (the degree on the MC) is moved towards it. Symbolically, we would say that the MC is directed to Mercury against the order of the signs (= conversely), because it is always the significator that is said to be directed
to something.
Planets, especially the luminaries, can be either significators or promissors, but the angles can only be significators (with a single exception, to do with the length of life), and aspect points can only be promissors.
When a promissor has latitude (that is, when it is a planet other than the sun), you can direct a significator either to its actual body in the sky or to its projected position on the ecliptic (= its zodiacal position). The former is a direction with latitude, the latter is one without latitude.
I hope this makes things a little clearer.