I learned to weld in 9th grade using an old Forney welder. It buzzed so loud I probably should have had ear protection.
The problem with AC and 7018 is that the 7018 is a short arc rod meaning that to weld right, the rod tip needs to be practically in the weld puddle but AC welders require a long arc length to keep the rod from sticking and if you get too long it will arc out. I don't know what they do to make the 7018 AC but it must be something that they changed so that it will run while holding a longer arc. I burned a lot of regular DC 7018 rods using my Dads old Lincoln Tombstone welder. I had to restart a lot because the rod would just quit burning or stick but I managed to build 2 ea. 40 foot x 8foot trailers with it that were still in service 20 years later hauling cotton to the gin.
The best way to get the rod back to serviceable length when a long piece of the flux is broken off is just to long arc the bare rod and then flip off the melted metal just as you get to the flux covered portion. It does take a little practice to be able to start the bare wire to arcing thought.