The FFF submethod states that words can be named by Form, Feel, and Function.
• Some examples of naming words by Form include (a) the leg of a chair, (b) the handle of a pot, (c) the branch of a family tree, (d) surfing the net or (e) brainstorming Some of these examples illustrate naming objects by form while other examples illustrate naming activities by form.
• A good punchy example distinguishing naming by form vs. function is pentagon-UN. The pentagon is named after the shape and form of the building while the United Nations is named after the function and purpose of the building. Although both these buildings have as a purpose world peace they are named differently.
• Examples of naming by feel/substance are glasses, hardship, ironing-board, plaster etc.

The FFF principle is a special case of the literary techniques of synechdoche-metonomy. These literary principles, universal to all languages, state that items can be named by related items, by parts of those items, or by good examples of those items. For example honey refers to anything sweet since honey is a good example of something sweet. Similarly hot refers to matters of love since the two are related. Todays Rashi can best be understood by applying these principles.

It immediately follows that a Succah with its thatched roof resembles in form a cloud. A cloud in turn is symbolic of prophecy as indicated in several verses (for example, Ex19-09, Jb40-06.). The idea here is that prophecy is not always transparent to the receiver. The vision appears murky like the vision through a cloud. Hence using the FFF principle the verselet I sat the Jews in clouds when I took them out of Egypt means I gave prophetic visions to the Jews when I took them out of Egypt. In fact Ex19-09 is a literal confirmation of this fact since God appeared in a cloud.

Advanced Rashi: There are Talmudic sources presenting controversy whether Succah means literally Succoth or whether it means prophecy. But as just seen no one disputes that the Jews received prophecy when they left Egypt and that prophecy is compared to a cloud! Similarly no one disputes that the Jews sat in Succoth. It would seem therefore that the controversy between the two sides is not as great as it appears. I am not going to explain what the controversy is today but I am pointing out that because of explicit biblical verses both sides believe that a) the Jews sat in Succoth and b) the Jews received prophecy.

Note also that Rashi literally says The Jews sat in clouds of glory. However clouds mean prophecy as I showed above citing Ex19-09. So I believe tbat Rashi uses clouds of glory to refer to prophecy.