Your friend with the bomb proof slag sounds like my stick welding with 6011, or 6010 5p for that matter, I see the welder at the bosses shop pop off peanut shell size pieces of slag with the bare end of the next rod 6010 5p. All ways wondered what I'm doing wrong. Years latter there is still slag often clinging to my welds. Rust proofing I like to think of it if I'm trying to be optimistic.
Eric