Thanks guys.
Worked on that front grill last night. Trying to find a way to do a rusty metal look without being "flaky brown rusty".
After a base of salted brown layers I first added some Vallejo aluminium to the grill, then wiped it back immediately with alcohol. This kinda left a shiny look that was pretty random. Then I added lots of really thin black and blue washes, really more like filters I guess, using Vallejo Acrylics and water. I just kept repeating / drying this process occasionally adding some Vallejo rust washes in splotches then more black, blue etc...
It was fun and turned out alright.