CAUTION: be careful what you use to clean metal. Some solvents will turn into deadly gasses when vaporized. And I do mean DEADLY. Please research what you use before using "any old solvent or cleaner". For a reference, search on the use of Brake Fluid as a solvent for cleaning welds. People have died from this and there is NO CURE. Another resource for you would be WeldingWeb.com. I am a hobby welder but found lots of great advice from professionals on the WeldingWeb forum (including the warning about what solvents to use).
The gasses you use depends on the metal you are welding. For general welding of ferrous metal, the 75/25 mix is great. Not so for Aluminum or Stainless. For Aluminum, you would likely want to invest in a Spool Gun but not all welders support them.
A good grinder with a wire wheel is a great tool to have for MIG. Your welds will improve dramatically the cleaner you can get your welding surface. Stick welding is a bit more forgiving when it comes to rusted/painted surfaces. A 6011 rod will almost weld water to rusty steel.......OK I am exaggerating just a little bit.
I would also have to agree with sticking with the composite blades in the chop saw. Just be aware that they could break up so keep the shields on the saw and your eyes. I like the full face shield when grinding or cutting.
Be safe and have fun.
