Yeah! What he said. I found epoxy and micro-balloons to be real hard to sand. Light weight spackling works really good in most cases and sands easy. When you need more strength, finish reson and micro-balloons works pretty good. Sands like hard balsa. I mix it up a to a consistancy between honey and tooth paste. Depends on where I need it. Thicker if it might run or droop.
Edwin