I work on old machines here with the help of 2 of my grandkids. Well they have learned that they are NOT allowed to work on Mommy's sewing machine at home. But the 2 year old worked on mommy's serger - yup he did the thread thing like you were talking about. He had a grand time. She still has it so it didn't fly out any windows. She still uses it so I assume it wasn't too hateful to re-thread. I think you start on one end and work toward the other. You set the tension just like you do any other sewing machine - not too tight and not too loose. Where I hate it is when you have to get that tension balanced. It's been a very long time since I fooled with a serger so maybe it wouldn't be so bad these days.