But personally, I'd drill the holes at each end, V it out a bit and leave it at that - no cleaning !! Why? Because its a fresh crack and should be clean. Trying to clean it could just make it worse. If its worth anything, why not take it to someone with a tig and have it done right. Mig welding aluminum is fine for high volume production but has no place where quality and durabilty are needed. And a good tig welder can be set up to "clean".
