Yup, MrP. is absolutely right, same method I use. The water acts to "clean" the sandpaper as it sands. As long as you keep the surface you are sanding wet, you're fine. There's really no 'trick' to it. It does get rather messy though. You'll have to see how your helm looks after hitting it w/ 600 grit, you may want to go w/ an even finer grit to get it ultra smooth. Hope that helps a bit, & good luck.