Thanks to readers who recommended putting an inductor in series, called an "arc stabilizer".Zan
and I made one from a transformer we scavenged from a dead microwave oven. We used this method
to chop out the secondary and wind 20 turns of 10-guage wire, which is all that would fit.
We left the primary intact, it doesn't affect the function here. An inductor gives the current "momentum" to blast through bits of flux and rust that get in the way. The arc sputters a lot less, welding is easier, and the welds are better.
I got a great Indian-made stinger (electrode holder) for $6 from harborfreight
and replaced one of the jumper cable clamps with that.
Then I welded some repairs on this very badly rusted boat trailer. Too pitted to grind clean very well. I used 1/8" 6011 rod at 36 volts and it was fabulous. I melted good deep welds into all that rusty metal. Very satisfying.
We've got a self-propelled welder!