Well, invisible path/ques can be tricky sometime
Mostly then if you dont make "prework" for it!
Before you start, NO guests should be there where you building invisible path, guests are allways in the way
Maybe there are a few ways to build invisibles path easy, my way is to build an normal path first.
So i have an good overview how the Q-Line/Exit is going. Other pathways i build later, when the Coaster is finished, exspically the custom supports are finished. An good option to have an little preview is with terrainpainting.
I use the same method than Silvarret and use the "sand" paint to show me myself where my laterly pathways could be run. When the "pathway-postions" are fix, build borders and other stuff. If this was done, than fill up all the empty-space between the path-borders iwth the invisible ones.
For the Q-Line/Exitway, the only differents are that you delete the original path and replace it with the invisible ones
After this whole work is done, let guests to this area!
For the Q-Line it's importent that the additinal mid-fences are right placed to avoid guest<->fence glitches!
Hope this helps you a little bit.
Lg Cheleste