Cure time, although important doesn't sound like your problem, that's more about shrinkage.... Adhesion issues are more likely the culprit, not sanding the surface on say something like melamine or using cheap paint. Clearcoat will be only as good as your base (meaning that will come off too) as for the C/p clear will scratch and start to look pretty rough in a short time. Plexy would be a better choice there, it too will scratch but was considered industry standard on some games... Personally... Jennifer would use a coating more suited to the task, such as automotive, or industrial.