I use automatic exposure-- I know if you are a professional photographer, you wont be satisfied with that, but I can tell you that the raw 4k video on AE with an ND filter is great. Just have to do a little color adjustment at edit.
Hi Robert,
welcome to the forum! Lot's of similar questions here, and a lot of good info has been put forth, so I'll just post a link to YolevonAllin's thread that would probably be a good starting place for you: http://www.phantompilots.com/threads/agree-dji-phantom-3-best-camera-settings-….46018/
after that, just get out, do some flying and recording, and see what works best for your situation.
Have fun!