A handful of grass used to scrub this mixture around should clean your pan very effectively and quickly
when you have washed the pan pour the water and residue into the edge of the fireplace, this area will already have been affected by the alkali in the ash. It also reduces the heat
in the ground under the fire and makes it easier to extinguish in the end.
Rinse with water and again pour it into the fireplace.
On the next rinse you can pour the water away elsewhere if you wish but not into the water source.
All too often I have seen people washing pans directly in streams or lakes only to pour the dirty water back into the clean source.
Always throw the water well back onto the land, this way the ground can filter out the organic materials,
reducing contamination of your source water.
To be really safe, for a final rinse use clean drinking water, or boil the water in the pan.
If I have no ash from a fire, more often than not I scrape the pan clean with a plastic “chef aid” and leave it until I have a fire to clean it properly.
Remember, it is not acceptable to leave food remains all over your campsite. You should leave no trace on the landscape. If you brought it with you you should take it home too.