I would use a bit of dish soap and then lots of clean water.
Here in the USA the chemicals they ate allowed to use are supposed to be environmentally friendly. But that doesn't account for a motorist with an oil leak.
Dish soap it is then. Hopefully the grit will help my hen's crop digest the food more quickly... at least until I can find pure grit in the capital. I know there are other backyarders in Quebec; if I can spot one, there's high chances they could tell me where they buy grit for their chickens.