About Touch Up
A broken WHITE LINE caused by Over-Polishing
Use Masking Tape to mask over the RED area. However, leave some WHITE area around around the Problem Area. Otherwise, the TOUCH-UP area would not be NATURAL at all.
I use a extra fine nozzle airbrush for this job. 0.18 mm. In addition, air pressure is about 0.5 bar. Since the air pressure is small, avoid using THICK paint. However, if there is too much THINNER, the paint will be too THIN, it is dangerous and may be easily going under the masking tape and dissolve the RED paint. So, please try it on a paper or other part first, make sure the concerntration is OK. Be patient, a thin layer over thin layer. Make sure sufficient time for paint to dry.
Remove the mask tape carefully
Give more time for the paint to dry, then a bit polishing. --- Done
Just a little sharing, don't take it too serious