I use Procreate for all my designing now. Although I have Adobe Illustrator, I still use an old cheap program called Print Shop to do all my resizing. I send my Procreate designs to iCloud or my Dropbox and then open them in Print Shop. There I can set the design onto a page with millimeter "rulers" and size it to whatever I want. I then print it onto plain paper, (in reverse, of course). Then I tape a properly sized piece of transparency film over the printed design and run it through the printer again. From that point it's a simple matter of using Tom White's solution on the gun or knife and rubbing the transfer onto the metal.