[conundrum]

Are you using paint, gundam markers, or something else?

Edit: When painting or using a marker, masking tape is your best friend. It gives you clean edges. If you do get paint/marker run off, quickly use a slightly moist paper towel to clean it off. A little bit of nail polish remover will also help to take it off.

When doing real fine lines, run your marker/paintbrush over it and then wipe with the wet towel. It should leave you with just the highlighted lines and no run over.