Do you just want to learn to control your sneezes? Or are you interested in the photosensitive effect directly? If the former I would encourage you to learn more direct control mechanism rather then using a external trigger like light.
edit: spelling
Primarily I was looking for an exercise in conditioning, any practical benefits are ancillary. If progress continues, I will not sneeze unless a specific trigger is present (staring at a very bright light); so it should be a passive benefit with no long-term upkeep. If you have better ways of control sneezing, I am interested in knowing them.
This is the fifth bimonthly What Are You Working On? thread. Previous threads are here. So here's the question:
What are you working on?
Here are some guidelines: