In all seriousness you could hose off the chassis of your amp. You just need to dry it out afterwords.
I am telling you, I did this to expensive test equipment that in all probability cost more than any amp you may happen to have.
Absolutely filthy dusty equipment was returned to almost new looking condition by the method I describe above.
Again, I am not suggesting that you do this, but the post was not meant as humor. I was paid to hose off and then oven dry equipment.
There is nothing in the chassis of your amp that would be damaged by some clean water and a good drying. BTW I am talking about an oven that was probably about 120 degrees F. We left the equipment in there for a few days.
I am not freaking kidding here! Been there done that!