Perfect responses! Your keypoint is here:
...creativity is creating a situation in the Genjutsu that will benefit you in the actual fight while your opponent is trapped in the Genjutsu, basically tricking him into thinking that he's required to perform a certain counter or action that is actually the opposite of what he should be doing so you gain the upper hand.
Many times, before we can decide on a proper countermeasure to a Genjutsu, we need to somehow
reason that it is a Genjutsu, and the more creative your idea is, the harder it could be for an opponent to actually realize it is a Genjutsu. You can't simply state in battle that you somehow escaped from it without first knowing it is in fact, a Genjutsu. With this, you can then come up with tricks and ideas that place your opponent into a corner however you wish, as said, the only limit is but your own imagination.
Genjutsu does not always require handseals, in fact some only need you to release your chakra and target it at your opponent or in a certan area. But you are indeed correct in stating that it tends to do mental damage (unless, of course, we are speaking of F-Ranks such as Izanagi or Izanami) and focuses on the psychological aspects of an opponent. Whenever using Genjutsu,
make sure you state how it affects the five senses because shinobis are able to gather information from all of their senses, so it is vital that you erase any chance of them doing so. Finally, you correct in stating that it interrupts the chakra flow. In fact, you target the enemy's brain (the prosencephalon structure) and the chakra that flows there - the process is carried out by you first releasing your chakra towards the opponent and then directly affecting their chakra system and then messing up their senses.
So, given that you now know how Genjutsu works, name as many ways as you can think of that allow you to escape or counter a Genjutsu.