Sounds like you're talking about the A/C--D/C buzz box. I used one for years and it did more than fine.
I only have one personal preference for Miller buzz boxes over Lincoln. That's the ability of the Miller to adjust by the amp instead of the five and ten amp adjustments Lincoln uses.
I once had a fella who taught welding tell me that his experience showed him that either you have it or you don't. Some people just pick it up and some never can.
The biggest mistake I see newbies doing is moving too fast. They've burned a hole and they become terrified that it will happen again. So they move entirely too fast after that.
You have to keep in mind it's not like using a calk gun, well mig running like most folks run it, can be. /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif What you're doing is melting a little off each side and then adding some more molten material to it so that you have something completely different but is a whole unit and no longer two halves. Think of it like a marriage I guess, a good one.
I once had a weldor explain the process as similar to making love. Hmmmmmmm how do I do I explain this for mixed company......????????? I guess, well no, okay, how about, no, awright, no........
The concept is that the molten metal part of the weld is like a part of the anatomy. And that it's natural condition is liquified on the edges while making love. You want that same liquification (bushism?) three hundred and sixty degrees while in the welding process.
BTW there are only two things that a weldor can't glue back together. The crack of dawn and a broken heart. And when it comes to gaps, if he can step across it, he can fill it.