i dont know what you want to know about the mig welding of aluminum but i have done it using several different machines..
i've used the cobramatic, Esab, an the miller and airco spool guns.Some say you can use a a miller 135 and push the wire thru the 10'conduit and gun but its hard to do.
aluminum wire swells and softens and is hard to push thur a 10' liner,so a spool gun makes it eaiser to weld only having to push it several inches.some make wire feeders and spool guns that will operate with portable gas welders an the larger stick welders..the miller 200 has a plug so you can just plg in a spool gun when its needed..argon is used as sheilding gas.Aluminum wire can't be run thru the same liner thats used with steel wire .as the aluminum will be contaminated.
look at this site www.millerwelds.com/education/tec_articles