I don't have any gouldians...yet.
I gave up on the commercial cage skirt, it does not go high enough to stop the seeds that are blown up when they fly. And the hanging birdbath creates another problem fitting it to the cage.
On my new cage, the combination of a solid back and top means the flapping blows the air out the side and front a lot more. I got some krinolen (sp?) from the fabric store and wrapped that around one of the cages to stop the feathers, might have to do same for the gouldians for the seed hulls.