I do have a question. How does one handle dynamic maps? Such as a lever lowering or raising water. Do you make two versions of the map or add the changes in transparent form?
That's a very good question to which there is unfortunately no universal answer. I used to be sure how to handle such cases but the more maps I made, the less certain I became.
Nowadays, if at all possible, I would try to do two maps: 1) the initial state as you first encounter it and 2) the finished state where everything has been changed/destroyed/revealed. I would personally try to avoid or limit instructions depicting how the changes are caused but that's mostly because I prefer aesthetic maps. Your mileage will vary if you're trying to make a visual walkthrough.
If the map is really simple though like an area with a few hidden paths, I'd probably make a single map with the hidden paths visible because the initial map doesn't depict a different state, just an incomplete one.
I hope I'm not leaving you with more questions than you had before!