Due to various health reasons I have been unable to hand wash the car for some years, but yesterday I noticed this on the RNS Wheel Arch return

The metal does not flex under a finger and thumb and is solid when 'poked' to its
just surface rust
I haven't done any body repairs for something like 40 years, and even then my painting skills were somewhat limited, so my thoughts are:-
1) Scrape/brush/sand the area as clean as I can
2) Paint on some
Krust3) Prime
4) Brush (not spray) on
Colour Matched Paint or
Paint Nuts(The reason I am thinking of painting it on is 1) I am lousy at spraying and 2) its an area thats not really on show)
Is that the best approach, or is there a better way to sort it out?
TiA