Woodsmith, after reading all the suggestions from the other members and I agree with most of them, here is something different and save you a few bucks. The cleaning is the most important overall, but instead of buying degreasers, solvents and such, just use vinegar. You say you used a s/s pad to clean with, thats good as long as you only use it on aluminum and always use a clean side or you're just rubbing contaminats back into the metal. After the pad, spray or brush it with vinegar, that will nutrilize the metal. Without a spool gun its hard to use the smaller size wire, really need .030 but to help absorb the heat from the bigger wire and give you more metal to work with get some aluminum rod, 1/8,5/32 and lay it between the tubes where you are going to weld, be sure to clean the rod too. I differ with a couple quotes here, you can make mig look as good as tig. I have been welding for over 40yrs and although tig is good, mig is faster, I hope this helps in some manner.