If you need to blow built up fuzz and other materials out of your sewing machines you can use an air compressor. The canned air that is used by people to clean computer keyboards, etc. contains chemical accelerants that can dissolve some lubrications in your machines (depending on what was used). If you aren't spraying a whole can on your machine everyday, I think it would survive a blast or two. (My husband works with a lot of electronic components and tells me the canned air can be used to clean electronic components. That is what is was designed to do.) Blowing fuzz out with your mouth isn't such a great idea although I catch myself doing it. There's a lot of moisture in breath that isn't very good for a machine.
I can't tell you any method will never cause a problem trying to clean out your machine but the last time I dragged mine into my dealer because the bobbin sensor wasn't working they whipped out a can of air. I just started laughing because I didn't use mine. If you are really worried, check with the guy that repairs your machines. If you don't know one, they are really great resources.