Also, you don't have to move the master layer on each spread individually. You can select the master layer on one document page, right-click, and choose Edit Linked. Then you can use the menu item Layer > Arrange > Move to Front. Then click on the Finish button. That will move the master layer to the top of the layer stack on all the spreads. Of course, that is a one-time action, so if you draw anything on a page after that, you need to ensure it gets inserted below the mast