For good and ill, I learned mostly from trial and error. One thing I did was to orient all the magnets on the suits/drone stands and weapons/drones so that they are universally interchangeable. I use the drone stands to orient the magnets as they would be in a suit's arm/shoulder and, after having to dig out a couple that went in the wrong way, I apply a dot of paint to identify which side should face out.
My magnets and bits are packed but I'll try to find the sizes.
I bought a dremel tool with a flex shaft and that works well to drill the holes and, with care, not fingers.