Just saw this thread. Not a pro weld **** type here. I'm proficient with mig, tig and even gas welding. Material prep and proper fitment are huge factors. HOWEVER if you cant see the puddle none of it matters. I have a few different helmets, I like the #10 on them all. For me its really about getting my body/head into a position that will allow me to see the puddle. If your running a bead and the gun or torch is blocking your view, your probably in the wrong position. Yes, flux core makes alot of smoke and does make it little more difficult to see. For me, once I can SEE the puddle and my material I have a much better chance of putting down in good bead with deep penetration.
If your welder is down on power, using a torch to put some heat into your weld joint is one way to work around it.
