Cheers guys! Boxcab you get about 30 minutes of easy working time, depending on the weather. Damp days are best. It can still be worked by re-wetting after that, but that's when you'll need tools like scrapers, although you can probably still smooth out small areas by rubbing it with a wet finger. Once it's completely dry it can be sanded. You can add acrylic paint too, but in my experience of adding acrylic tube paints, and somewhat contrary to the manufacturer's advice, it really hastens the drying. You have to work like crazy to get it shaped.