My Auntie told me about this last night, she remembers when she was young the old ladies used to do this. I tried it this morning when going out to put food out for the birds and it seemed to work.
I dont recommend the cat litter tip. I did this last year and it turned into horrid grey mush that stuck to the tread of our shoes like glue and was tramped into the house.
I think it was only on anglia news but people in a shop that had run out of grit was shredding dishwasher tablets and selling that as it worked like grit.