Wet and dry sandpaper. Some sandpaper is dry only and will come apart if wet, wet n dry is designed to be used wet or dry and in this case I would use it wet.

Edit for more clarity; I would have a bucket of soapy warm water with me and would regularly dunk the sandpaper and clear it out so it doesn’t clog. Might not be needed, hard to tell how much sanding is needed from pics, but it will massively extend the life of the sandpaper and it’s effectiveness to keep it from getting full of gunk.