I just went through my brewing notebook, looking for measurements collected by hydrometer and refractometer at the same moment in a brew session. With 16 measurements from actual brew sessions, I come out with a WRI correction factor of 1.042, which seems to be well within the expected range. This exercise alone reminds me that I need to be much more stringent in collecting data at the appropriate times, and writing that information in my book. I found some holes in my records.If you have OG measurements from both hydrometer and refractometer that will work. If not, you can use the WRI average as you collect samples. You may be off a point or 2, but it's better than no readings at all.
I have to give props to my wife, who is more tech savvy than I, for figuring out how to get the table to work on my iPad.