In reply to The Lemming:
i just worked my way through a course from "creative cow" on youtube.
don't know what version you have, but i suspect the basics are the same for most versions.
although it's specifically talking about protune from a gopro, the point of the video is color correction... hope that points you in the right direction.
doesn't answer your question about ND filters of course, sorry. i just use a fairly basic set at the moment. they are rubbish quality but good enough for what i need at the moment