Hi Sharon, no top coat needed with this paint! It’s also on my exterior door – but keep in mind it’s protected from direct elements because of the porch. But I have a feeling it would be ok. For the interior doors it’s super durable, and such a pretty matte finish. Here is a blog post: https://www.snazzylittlethings.com/black-interior-doors/ — I apply it using a foam roller with a 2″ nylon paint brush.