This is terrible advise. I have hundreds of succulents and do not recommend following this advise.
Succulents do not need soil or anything else that retains excess moisture. Top dressing increases the chances of root rot by retaining too much moisture, and in no way does anything to prevent root rot. Too much or too frequent watering is the leading cause of death for succulents.
When watering succulents, saturate the soil (so water is dripping from the drainage hole) then, let the soil dry completely, wait a week, and water again in the same manner. In addition, I suggest using terracotta pots to allow the soil to breath and prevent trapping excess water.