Dan
I should have pointed out that my advice to use WD-40 was for parts that were to remain natural and need to be protected from rust.
Obviously a person doesn't want to oil down anything that's to be painted.
I think you have over-thought your predicament. Just re-dip your axle housing in the citric acid treatment. It's a great cleaner as well as rust remover. It'll take off the WD-40. But rinse with hot water this time and skip the wd40! Dry thoroughly and apply primer and paint.
Merry Christmas and Happy New Year!
Doug