Is it actual automotive quality paint? I paint cars for a living so I can help if I know what kind of paint it is? Is a base coat clear coat system? Acrylic urethane? Alkyd enamel? It makes a huge difference in dry times. If it's a BCC system then 1hr would be way more than enough to mask, if Urethane it would be at least 16hrs if alkyd it would be at least 24 hours.