Spent Wednesday covering everything with what looked like Cornish china clay, but was far less romantic: Hobbycraft air-drying modelling clay. It gets everywhere. However, I filled the 'four foot' almost to my satisfaction, and must now pluck up courage to attempt not to glue up a point. Thankfully, it takes about a fort-night to dry, and it is freezing cold and snowing outside, so a good reason to find something else to do, or at least start wondering whether the cracks will show under a couple of layers of acrylic paint.
Such a shame I had to dismantle everything for this task. It all looks so offensively untidy!