A couple years ago I made some birdhouses out of dried gourds,
Now normally I scoff at over-protective measures, but when I was at the farm digging through the gourds to pick out the shapes I wanted I started coughing. And I have perfectly good lungs. The stuff on these gourds is not for the feint of
The best way to get the dirt, dust and mold off these things is to soak them in a big bucket of water with dishwashing liquid and a small amount of bleach to loosen the stuff and keep it non-airborne.
Some people suggest wearing a respirator or mask while handling the gourds. I just held my breath.
After soaking them for two hours, I scrubbed them with a nylon covered kitchen sponge and the gunk came off fairly easily. Throw away the sponge after you use it on the gourds, because you don't want that stuff on your dishes.