I had to do some similar touchups on one of my USAAF Mustangs, Glorfindel.  I had a couple of spots where masking tape lifted some paint.   I was able to repair this without remasking and spraying, by mixing a thinned mixture of the color and brushing it on.  It was acrylic, so I was able to use the layering technique that guys do with figures, building up the color with repeated thin layers, till it looked right.