Q&A for How to Drill a Clay Pot

This would not work. Clay is very brittle and will shatter. You need some type of orbital abrasive to wear through the clay. Also, that abrasive will work best with water as a lubricant. A carbide drill, a diamond grinder bit, or a Dremel tool would work much better.

Follow the steps here and use a drill bit bigger than the current size of the hole.

Assuming you don't want to break the whole pot, you can't reasonably expect to use a nail and hammer. A drill is a much safer option.

It depends on the plant, as some need more holes for better drainage. Ask your local farmer or plant expert for guidance.

It depends on what kind of pain you use and if it was glazed or varnished with a waterproof product. If it's a water-based paint on an unglazed pot, then yes, it's going to be damaged by water. If it's a glazed pot that was painted before glazing, then it should be fine. If it was primed before painting and then varnished with a waterproof product, it should be fine. Consider doing a spot test in an area of the pot that is relatively hidden and testing if the water damages the area.