The dynamic structure involves the articulation of each hexameter verse into two or three word segments by word breaks, which generally do not coincide with foot-endings.
The word-breaks that articulate the hexameter are the caesuras, whether
–after the long position of the third foot (masculine or penthemimeral caesura),
–the first short position of the third foot (feminine caesura) or
–after the long position of the fourth foot (hephthemimeral caesura, often with another caesura after the long position of the second foot).
There is also sometimes a word-break that corresponds to a foot-ending after the fourth foot, known as the “bucolic dieresis.”
The dynamical structure of the hexameter consists of the interplay of these word-breaks against the formal metrical pattern of long and short syllables divided into feet.
These principles are at work in both Latin and Greek hexameters. In Latin hexameters, however, there is another factor at play: namely, the stress accents of the Latin language, which tend to conflict with the pattern of long and short syllables in the first part of the verse and resolve into harmony towards the end of the verse, especially when a bucolic dieresis occurs after the fourth foot and the fifth foot is not spondaic, yielding the “Adonic” pattern, _ u u | _ X.
You will pick up a feeling for these patterns if you read metrically, paying attention to caesuras. You should always read metrically either aloud or at least in your head (but in Latin trying to give effect to word accents that conflict with the pattern of long and short syllables – not easy to do at first, and I don’t always manage to do it properly myself).
The sound-painting Aetos mentions (e.g., galloping horses) is from time to time imposed on top of the dynamical structure of the hexameter described above, as are effects such as internal rhyme and alliteration.
If you write out the scansion of 10-20 verses a day for a while, making sure to mark the caesuras, and then read them aloud, you will get the patterns in your brain and they will come naturally as you read, and you will hear the music of the hexameter.