[Fixer]

I think you should do it the right way or save yourself the trouble and money. It won't blend. The bumper cover on the Lincoln would need to be taken off and taken to a honest paint shop. They do exist.

The 928 that has rust at rear quarter glass is a pro job also. The entire rear quarter would need painting as well as blending into the door on that side.
Can't be done with an air brush.