[yotatechie04]

I've had similiar problems with my Camry when touching up. I attempted to use the fiberglass pen as well, and did good for so long until it got to the bottom. I think that if you do decide to go ahead and touch it up from that layer it will eventually show through or bubble up. I ended up using a really fine grit sandpaper to remove the remaining rust, which if used very carefully, it will work effectively. Other than that, if you decide to use a rough sandpaper, you'll more than likely have to repaint the whole panel.