Dan,
I just found this thread, but you've gotten some decent, well-informed advice so far. I'm a Union Boilermaker, as in (at a minimum) I weld all three major processes (TIG, stick & MIG) on most metals for a living. I'm a tube welder (processes usually requiring TIG and stick together in all positions, unlimited thickness) with many certs. Again, good advice from the guys. If and when you run into trouble/throw your first hood, breaking it, feel free to give me a call if you'd like: ( 8 5 O ) 7 O 2 - - 3 7 O 2. Or anyone else on here, for that matter. We all have questions sometime, even me (and I'm supposed to be the professional), so don't ever feel bad. We're always learning and getting better.
As a side note, go to weldingtipsandtricks.com It's probably the most informative website I've seen, whether you're a beginner or a pro.
It's not easy trying to learn on your own, like you are, Dan, but with sufficient practice, time, practice, patience, practice and research (and practice), you can fill those voids without any porosity.
Like it's been said, stick's the hardest to learn. It sticks like crazy when you're trying to learn and sometimes when you're a pro, too. Practice your starts on thick plates with cheaper 7018 rod. Scratch starts are done by striking the rod tip like a match -keep it moving, long arc it if need be and shorten your arc slowly till you get the hang of it. Clean off the slag on the end of your rod between starts by taking it out of your stinger and running it across a heavy file until you see "the shiny". That'll help. Turn your heat up to help from sticking, but if it's too hot and you don't keep moving, you'll burn through/spatter everywhere/leave undercut and it won't run smooth. Stay away from AC. Run DC and "reverse" polarity (ground: - & stinger: +). (TIG will be opposite in DC for what you need.) The rods mentioned are fine, but practice with anything cheap, first. 7018 is easiest of carbon steel. 309 is easy to find and is good for stainless and carbon to stainless, but practice cheap first. Make sure you aren't going too fast by dragging your rod out of the puddle before feeding it/filling it, otherwise, you'll be sucking the puddle away from that area, leaving undercut. Pause and fill it before moving on. Steady and consistent. Watch the puddle, keeping an eye on where you're going. Too slow, and you'll either burn through or leave overfill/leave a bead too high, thus increasing the risk of "roll-over", thus trapping slag in/under the weld bead. Good welding is from the practice of finding the perfect medium in EVERYTHING, keeping it all consistent, all at once: heat, arc length (and keep it the same length), rod angle, rod speed, manipulation size, comfortable body position, etc. You've got to find the perfect middle ground in all these things (and more things) ALL AT THE SAME TIME ...and with confidence. Stops and starts are tough, too, as there's a lot that can go wrong, messing your best work up. It aint easy. Don't weld angry. Breathe. Talk to yourself. Think about what you did wrong and how to do it different. This is where you need somebody to show you what you did and how to do fix it before it becomes a bad habit. A beer helps, but not 6.
That said, even though stick should be learned first, TIG is easier, cleaner and safer (in that it can be done in a white business suit without catching the shop on fire or burning your nice, PPG Aquapon epoxy garage floor -yes, less fire blanket required). Just don't clean anything with brake cleaner and light up an arc on it... you'll get phosgene poisoning and die slowly and painfully. A good thing about TIG is thre's no real slag to deal with and what you see while you're welding is exactly what you're gonna get. You can practice TIG with brazing, but remember, brazing isn't welding. It's just adhering metal to the base metal. Welding is heating the base metal BEYOND its melting point to make a homogenous/soild metal for much better fusion/tie-in. If it's not, it's called all kinds of names, but that's for guys that say they're real weldors. For you, it's all called practice, so fire away. No worries. Post some pics, regardless how bad it looks. You'll only get better, so we'll all get a chance to see improvement. Feel free to call anytime. If I don't answer, I'll call right back (unless I'm on a job somewhere out of state, which will be late August, this time of year).
Sorry for the length, but it's welding... c'mon. A whole book isn't enough, y'know? It's time under the hood. Like driving is seat time. Shooting is trigger time, etc. You just need to know where ALL those happy mediums are to call it a science and an art. Don't work angry... Don't work drunk.
Ivan