Start wiping! You will be amazed how easily that scum wipes away. Keep turning your towel as needed to a clean section that is still moist to be as effective as possible. It’s totally OK to let it sit on tough areas for a while. I’ve worked on boats that had it so bad it was about an eighth of an inch thick off the boat. It took some scrubbing, but it all came off. After it dries you will see what looks like yellow staining on your topside or bottom that might look alarming, but don’t worry. Grab your spray bottle and you can literally watch it disappear when you spray it. It’s actually pretty cool. I recommend a spray bottle if you have bottom paint because you can wipe up the water/acid before too much hits your bottom paint and causes a reaction… especially if you use something high in metal like VC17 which is copper. You will need to wipe a few times until the acid is all gone and the yellow goes away…but again, you’ll see it just disappear every time you spray it again. If your hull is bare, grab that hose and rinse it, baby!