HELP 😣

My beautiful gymnocalycium saglionis broke off from its root. I don’t normally water through Christmas time and I certainly wasn’t aware of watering it but last night when I was looking too see if it was gonna need a repot this season, it broke off from its root 💔

The bottom of the cactus isn’t mushy the few roots that are left don’t seem mushy either. I did spray it against mealy bugs last night after it broken off as per caution.

Everywhere generally says keep in shaded area for a few days allow root to dry and place in new soil. Now is there anything else I should do? And is the white stuff something to worry about?