I just soak the gourds in warm water and dish soap to loosen the mold. If it's hard to get off after soaking, I use a steel wool pad. Let them dry and they are ready to paint. I use acrylic paints on mine and seal them if they are going to be outside. Good luck.

Yep, what Frances said. You can wipe them down with a bleach solution after washing and scrubbing but I never felt the need to. Just make sure you let them dry thoroughly before you paint.

It's kind of satisfying to see how pretty they are under that gunk!

I wash mine, let them dry, and then sand them with a sander called a sand-o-flex (made by Merit). It has little "fingers" of sandpaper on a wheel that turns. It's not the sanding wheel that just has flaps of sandpaper, these flaps are divided into little strips and is softer. Works great on wood, and gourds, and I have used it on metal to take off the rust. However, it is getting harder and harder to find the refills!