...I had no filming experience. Had had is a correct construction under other circumstances.

There is one small mistake: "not filming experience" should be "no filming experience." A more common wording is "I had not had any experience." Yes. This is a correct use of the past perfect to clearly indicate the sequence of two states or actions in the past. Some native speakers omit this distinction in spoken English. For writing, use the past perfect. For speaking, match the people around you. More information: https://www.englishpage.com/verbpage/pastperfect.html

1) Yes "had had" is correct. They are you auxiliary and primary verbs, respectively. 2) You can just as easily use the simple past here because of your use of "before". You would however need to use the past perfect in a sentence such as, "I had not yet eaten when I arrived at work yesterday."

So it might be better to say "I had no experience in filming " or "I hadn't any filming experience" I hope that's helpful:)