Blue Aran hasn't had any black Tuffcab for months. Your best bet is to get a litre tin of Armacab from Penn Elcom. It's very similar to Tuffcab but thicker in consistency and with a higher pigment content. It'll cost £27 delivered. To get a decent finish, you'll need the foam rollers from Blue Aran. Unfortunately, they're out of stock of those as well but they're due in mid-December according to the website.
In current weather conditions, it'll take some time to dry. So, leave each coat to dry overnight - and don't allow the paint to freeze, as it will then be useless.