To seal in those little spots, we used Eastwood's Rust Encapsulator. It is made to seal and stop rust and corrosion from spreading, preventing rust creep. It's epoxy-fortified for better adhesion and topcoat compatibility, and the low-VOC formula is acceptable in California. This ends the rust treatment, but because all the little rust craters are low spots this will also be the first line of filler. We let it dry and then hit it with a block to smooth it out.