The manual suggested 2-3litres per minute. I set it to 3 with the trigger pulled. That said I am working outside so that probably isn't helping, I'll up it to more like 4-6.There’s not a huge amount of gas coverage, as evidenced by the smoky residue left around the welds, but it’s not so bad that they’re all porous & rough-looking, plus those mini-regs are notoriously stingy with flow, probably mainly so that the gas lasts a tiny bit longer!
Another thing I am probably getting wrong is that whilst I am trying to keep the gun about 1/2 from the work surface I do have a tendency to wonder - I guess that's inexperience.