When wet sanding, it’s very important to use guide coat between grits. The point is so you don’t miss any sand scratches from the previous grit.
In order to not miss anything, using enough light really matters, probably more than you might expect.
I really like using a spot light on the area you’re sanding, this type of light really highlights the guide coat.
•A quick tip, wetting the panel down is when you can see the guide coat. If the panel is dry, you really won’t see anything
You can see in the picture below where there is still remaining guide coat. That has to be sanded until it’s completely gone.