Re: wet rudder and winter time comming soon
I use a bit, say 1/4" to 3/8", not a hole saw. The holes do not have to be big, but you'll need at least two. You are drilling through the fibreglass skin, into the foam core (which is likely saturated). Drill the main drain hole at the lowest point, but you may have to drill a number to get all the water. In my case I found pockets of water trapped, so ended up drilling a whole bunch up the side.
If the holes are small, and there is still foam backing, you can just plug with thickened epoxy. I hit voids, so had to grind out the area, and rebuild the fibreglass just as you would with any hull hole. Hopefully not necessary in your case.
Why go fast, when you can go slow.