A golf ball-size amount of mousse is recommended; if your hair is long, double that (or more). Mousse should be used on hair which is 50% dry, not on very wet hair. When applying, first spread the mousse around your palms and work through with fingers or a comb from root to ends. You’re trying to form a film over your hair to hold it in place while it dries and after, so good distribution is key for good hold.
Mousse application for better distribution and hold.