I got some kill rust to treat a spot i found. Bunnings $12.00
I scraped off the ;loose stuff then brushed on the kill rust, and left it to dry. 1 day.
Went back applied more kill rust today after wiping off the white stuff from the kill rust.
When that was dry same process whipe off the white stuff and put etch primer on with a small artists brush.
Over that when it dried i have put 2 coats of touch up paint.
Ill leave it for a while and see how it goes.
Then ill cover it with more touch up paint if it looks ok.
If it dont look the goods ill have to involve an expert.