The tutorial is based on AA stuff, never added any steel for curing to their solution. I run it about 190 to 200 degrees and 10 to 15 minutes gives you a gray color and 35 minutes a charcoal color. After you dunk your parts, take a look after only 5 minutes and you're 80% there already. I've left stuff in there for an hour and after 35 minutes you really don't see much difference. The instructions say 185 degrees, but I run mine at 190 to 200 because throwing large cold parts in there brings the temp down about 5 to 10 degrees so runnng at 190 to 200 ensures that it stays above 185 at all times. On a large tank this probably has no impact, but my tank is only 48x8x8.
Some guys report that the Brownells gives a better finish, but the AA stuff is holding up well and is not thin. On my gun I glass beaded all the internals and parked and they are about 3 years old now and the finish is still hanging in there...of course with all the wheel bearing grease I pack in there I doubt there's any metal to metal contact anyway LOL

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I don't know whose solution Ohio Ordnance uses, but on my '28 and BAR that stuff is thick as three coats of enamel paint...good stuff.
BTW, my solution is three years old and I just add a little more concetrate once in awhile and it's good to go.
The top photo is my gun parts cooked for about 30 minutes and the second photo is a friends at about 15 to 20 minutes.