Youtube and practice (for both the airbrushing and the brush painting). And even then, I would say I still don't know a lot about it (definitely deficient in that practice part).
This ZakuAurelius video series is pretty good at showing you the full process for gunpla specifically
For brush painting, I essentially transferred skills I learned for miniature painting, and any good video for that will help you with the other. Mr. Hobby Gundam Color paints (semi-gloss) tend to dry to a similar gloss as Bandai's plastic, so I thin those with either a bit of Isopropyl alcohol, Mr. Hobby Acrysion Thinner, or Mr. Color Leveling Thinner.
Youtube and practice (for both the airbrushing and the brush painting). And even then, I would say I still don't know a lot about it (definitely deficient in that practice part).
Some specific videos I watched were:
For brush painting, I essentially transferred skills I learned for miniature painting, and any good video for that will help you with the other. Mr. Hobby Gundam Color paints (semi-gloss) tend to dry to a similar gloss as Bandai's plastic, so I thin those with either a bit of Isopropyl alcohol, Mr. Hobby Acrysion Thinner, or Mr. Color Leveling Thinner.
That's fantastic, thanks for the links!