I have a doitsu kohaku female that has been spurting out eggs for the past 3 years, but I've never planned ahead enough in the past to really have a means to breed them. This year, I bought a 150 gal aquarium back in September and had 4 of my smaller koi living in it, in preparation for spawning day. I also made my own spawning brushes by taking two lengths of 1/2" PVC, cutting lengths of braided polypropylene rope, zip tied them to the PVC and de-stranded them.
05/20/19 - Spawning took place. The Kumonryu(?) did about 90% of the chasing and bumping into the female, the sanke came in a bit toward the end. There are also a kujaku and doitsu kujaku that are of breeding age that may have got in there as well. Transferred small koi from tank to pond and pulled spawning ropes into the tank.
05/23-Left for work in the morning, no fish. Came home from work that evening, thousands of fish! Pulled the ropes from the tank and placed them in a ~250gal pond by my front door. Did a pretty massive water change to reduce ammonia and vacuum out eggs - lost quite a bit of baby fish in the process.
I will try to keep this updated. I am sure they will quickly outgrow their 150 gal home, so i plan to utilize the front yard pond as well as a 1,200 gallon inflatable pool that I have in the attic.