You said "I haven't really prepared, but I would have thought that doing some kind of preparation (maybe lots of lumosity games or something, or more regular practice) would be good, as it would distinguish between lower than expected scores showing up because my brain is injured, or simply because I'm not as sharp from disuse for the past 7 months."

This does not make sense. Trying to prepare will only make the scores confusing. The tests have been researched, often over decades, to quantify problems. None of them have been normalized for the changes that may be due to Lumosity or other brain training. Plus, Lumosity and such create a familiarity with the activities used to gauge brain function. This 'learning how to do the task' interferes with the scoring.

I have had three plus NPA's. I have learned how to do some of the tasks better than I would have done them without prior experience.

The Trail Making Test is worthless for me. I have learned work-arounds so I can do it quite fast. Without these work-arounds, my scores were much different.