This is really tough to explain, I'll do my best. sorry for the large image. Didn't know how else to explain it.
Click the link to see a screenshot of my timeline.
Video 5 is a white animated box that simply masks the black linework on video 4. The white box is animated so the lines gradually apear. Video 5 is copied onto video 3 with the same motion to have the same masking over video 2 which is a colored base of the same shapes.
I want to have video 4 (the line work) multiply over video 2 (the colored base). I have figured out how to do that several ways by using some of the channel video effects with multiply. The problem is, with every option I tried, the effect requires a source (video 2-the colored base) for the multiplied effect. The effect uses that source the entire length of the clip--elimnating the white animated mask that covers video 2 (the colored base).
Is there a way to avoid that? Am I making ANY sense?
Just thinking here, as I have not done this and do not have the time to put it to the test, but:
Have you looked into Effects>Video Effects>Arithmatic and Compound Artithmatic? Also, I'd think that your "reveal Clip, the white one, could more easily be employed and Keyframed as a Track Matte Key. Might be worth a look.
PS neat Project, by the way