No, you don't have to wash it out. I actually leave it in until wash day (once/2 weeks).
As for the white film, just rub it in very well and you won't have it. Avoid getting it on your actual hair as it makes it dull and greasy looking (but I wear wigs so I don't care much personally).
It has no particular scent so it isn't noticeable to others in that sense btw.

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