What should I do about a paint film that's been spotted by rain before it fully dried?

There's only one way to remove depressions or surface blemishes caused by rain spotting. Clean down the surfaces to remove all dirt, grease and surface contaminants. Then rub down the surfaces with Wet & Dry abrasion, using water or a suitable solvent. Finally, rinse down and allow to dry thoroughly before applying a new coat of paint.