Re: the landspeeder shadow. There's a lot more going on in that shot than just petroleum jelly (if in fact there is any. I think Lucas was talking about different, locked-off shots and possibly an abandoned technique). If you oversaturate the color you can see that the orange blur is the vehicle's real shadow, painted out frame-by-frame with an animated shadow composited below it. They positioned the animated shadow lower so that daylight would be visible under the hull, but unless the speeder is suddenly a lot higher off the ground that means that the shadow is being cast towards the camera while all the other (real) shadows in the shot recede into the background. The SE and DVD versions have the same problem.

I mean OK, two suns, but really.