this is an older article but the methods probably haven't changed...

https://hubpages.com/animals/How-to-Breed-Shubunkin-Goldfish

any time you have aquarium or pond fish that are likely to spawn, it's a pretty big job to save the fry. when i had my reef tank, my clown fish spawned every few weeks for years. i never did see the fry because they always got eaten by the other fish as soon as they hatched.

I had koi and one shubunkin in a pond a couple decades ago (putting in a new pond in a new home right now, for shubumkin only). I can't really add more, but my koi also spawned regularly, and the eggs were always eaten up quickly... I had quite a few underwater plants that also floated to the top of the water level which provided a good hiding place for the fry, and that year had one koi fry live (out of hundreds and hundreds). I just crushed the koi food and sprinkled it into the top plants where I most often saw it. It did grow up : ) I considered breeding actively for about 2 minutes, ha ha, then realized it was a bit more than I cared to attempt. Wishing you the best in you venture!