Have you watched all The Soap Challenge Club videos from when they did it that month? There are a lot of them, more than normal it seems! Lol! That one intimidated me for sure & I’ve never tried it, so no help here. Good luck though, it’s soooo pretty!
Don't look at the soap in the mould, no matter how tempting it is to watch the pour. Instead, focus your eyes on where the batter kisses out of the jug else you'll end up with blobs of colour rather than the gorgeous feathering.
I do think this technique works best in a slab mold, especially if you want to pour into the center and have the batter swirl out from there. You can do a 'traveling' kiss pour which gives a different effect but is still pretty. Pour slowly and keep your eyes on the streams rather than the mold as @CpnDouchette mentioned. Choose complimentary colors, but with good contrast, so you don't end up with mud.
Lisa Cunningham of I Dream in Soap has a couple of good videos showing how various pours look. She ended up with a layered soap, which was lovely.