what welding helmet to use

I would NOT recommend a Harbor-freight, auto-darkening or otherwise. Your eyesight is not an area to cut corners on, and I've had to use them at work before (henceforth I bring in my own Miller Performance Series auto-darkening).

The cheap autodarkening helmets will quit at the wrong time and flash the hell out of your eyes, and if you're tigging, they are spotty about reacting. The glass used in welding protection is heavily doped to accommodate the correct/damaging light frequencies, and the Chinese-made lenses don't have the quality control to guarantee safety.