cure for bulldust

I would suggest any mild solution containing bleach or citric acid.

The suggested method before was a citrus based cleaner. If you have access to a high pressure cleaner, that does the job also, BUT the high pressure can allow moisture to get into places it is not meant to and the decals don't like it.

The other option is to just leave it, as it shows that you are using your BT for where it was designed to travel, and it will only return the next time you travel in those conditions. Wait until you get over to WA and into the REAL red dusty conditions.

try thr new orange oil based cleaners available from the s/market,,they are really good

We always use Wax and Grease remover. It is available from Auto shops that sell paint . sometimes called Prepsol Pyrites Pete