[AluminumWelder]

Just find something to prop your hand/arm against. a metal pipe with some legs on each end with magnet feet. You might need to make a few for various lengths or just move the pipe down every so often. Some people are gonna say it's a cruthc, but who cares, just do what works for you.

another thing that helps is to use your other hand to hold your forearm and give it support. I even used some keyboard forearm rests on my welding table to help get me get smoother motion and others here do to, that is how I got the idea!