Filling your head during Weekly Reviews.
In my opinion a good Weekly Review done weekly is part of the answer since during this process you review all the lists and learn what's on them. No, you don't have to remember every item but during a mindful review you notice the important Projects and Next Actions.
@Today list is useful but optional. It can be created during short daily review of your @context lists.
I think that GTD is not about emptying your head (it's just the first part of the workflow). GTD is about filling it again during Weekly Reviews with knowledge that helps your intuition to work properly.
Pozdrawiam i życzę sukcesów.