He's messing with your head. He likely wants you to make a mess of it so he you end up taking it to him to fix. All Metal is an aluminum filler and not a product you want to use, unless you are an expert technician and know exactly why you are using this particular product.
Get a good gallon of Evercoat Rage Gold or similar and have a much easier time with it than you ever would with All Metal.
Well he won't be getting it to fix if I try that, because he closed his shop. As I mentioned, I haven't gotten to filler yet, so will research more before starting. I do have some experience using filler, but it was about 50 years ago.
Thanks