While applying a final coat over a flat poster-colour background, the previous strokes begin to dissolve. What is the most suitable procedure?

Correct answer: Use paint of suitable consistency and apply it with a few controlled strokes

Poster colour is water-based, so repeated wet brushing can soften and disturb a dried layer. A coat of suitable consistency applied in a few controlled strokes reduces excess water and friction. More water or rubbing is likely to make the problem worse.