If you wait a little longer, as
@MACH5 suggests, ie til you can see very little moss it will be able to take more sun, therefore producing even more root mass before it shuts down for the year.
On separation, insert into a black plastic pot (don't use a pond basket or colander) and pour a good quality substrate around it. Pre puncture 4 holes in the pot & guy wire securely so it cannot move. Don't touch the roots for at least a year after separation. After this time I gently tease out the moss with a wooden skewer, replacing any voids with substrate. Training starts 2 years after separation when I'm confident it's strong. This is a safe approach that has worked consistently well for me.