For Nigella's Ultimate Christmas Pudding could the Crisco be pulsed with the flour in a food processor like in pastry dough? I could not find suet as I live in Alberta, Canada and the frozen Crisco was difficult to work with.
Nigella's Ultimate Christmas Pudding uses traditional suet, which is usually sold ready shredded and dusted with a little flour. We do appreciate that it is difficult to buy outside of the UK and have tested the pudding with grated vegetable shortening (such as Crisco) as an alternative. As the vegetable shortening is soft even when chilled, it needs to be frozen before being coarsely grated. It is a slightly fiddly process but unfortunately pulsing the vegetable shortening in a food processor with flour doesn't produce a great result as there is a larger quantity of shortening (150g) than flour (100g); as the shortening is soft you can end up with a sticky mass, particularly as the blade of the food processor will tend to warm up the ingredients as it works.
You could try cutting the shortening into very small cubes, with a sharp knife dipped in flour, and then using it, though this is still quite a fiddly process. It is also possible to use butter instead of shortening in the pudding. You will still need to grate the butter, but it is slightly easier to work with as it is firm when chilled. You may still need to chill the block of butter again halfway through grating and we would suggest freezing the grated butter before using it in the pudding.