I cut offsets in winter every year and prepare for the rooting carried out in spring.
The photo is offsets of Turbinicarpus valdezianus under drying process.
I spend almost 2 months for the drying.
Drying agent of cutting faces is garden-lime, not use any rooting hormone.
From my experience, the diameter of offset more than 30 mm shows a good success rate of rooting.
I will set up for rooting in early September.