I use a slow wire speed, small wire and the stitch welding technique. Short burst, well penetrated tacks. It takes a while but oh can end up with a decent looking weld with good penatration.
For mig overhead, I've found this to be the best way. Stitch welds do not build up a big enough puddle to drop if you keep the heat and wire speed down lower. I'll do a sort of "1/4 moon" weld, a quick half circle that builds just enough heat to melt the parent metals and add some wire for for the filling/joining. A quick stop after the single stitch weld, just enough to let it solidify, then on to the next stitch weld. It works very well, but still takes some practice like any welding. I just did a bunch of overhead on my truck welding up my hitch, supports and braces. The most important thing though, is a
VERY good welding cape and cap, and make sure your sleeves are tucked into your gloves!
