How do wrestlers such as Eddie Gilbert throw fire ?

It is an old magic trick called flash paper. Flash paper is chemically treated paper that burns up with no smoke or ash. The wrestler uses a wad of the paper, and ignites it, usually with a cigarette lighter, and “throws fire”. Wrestlers like Eddie Gilbert made it pretty obvious that he was using a lighter, while others, like the Sheik in his prime, used a little slight of hand to try and make it seem as if the fire magically appeared.