This is the third and final coat of primer-surfacer. By this time, the shape is correct and there are no flaws. We sand this final coat down with 600-grit for a uniform texture. No bodywork should show through at this point. Should we break through the surfacer, there would be a visible texture change and it will most likely show up in the final paint. Better to fix it now, while it is easy to work than to have to work twice as hard to fix a paint blemish.