The Vaseline thing does confuse me. I assumed it was on the plate, but the SE doesn't show it. Maybe that was an intermediate optical effect before they duped the ground on top of the wheels and created that discoloration? (Yes, as described in the interview I quoted, that orange or pink blob was an optical that ended up not matching the color of the live plate. (Notice the white lines around the guy's legs when he walks in front of it. That's where they rotoscoped him. And the footage must have been blurry by the time it got to that pass, because look at how eaten away his legs look. Looks like they had to sort of guess the outline, probably because the shape was so vague.)

But yeah, I see how it follows the speeder. And actually...maybe it was in camera but they digitally sharpened for the SE? I swear I can still see a little diffusion on the remaining original bottom of the speeder.

Not sure about the mirror. The pickup shots done in California (Look, there's a droid on the scanner) used the mirror, but notice that when they're going to Mos Eisley the speeder is behind a rock outcropping. That indicates to me that they hadn't hit upon the mirror trick while in Tunisia.