E head nail, use a marker to draw on clip outline and "let" them in. There's a tool for setting the nails but a punch will do as well. Charge double what you would for steel. They don't heat well in the forge, gas or coal. If you do put hem in the forge, wrap in aluminum foil. Then set steel/ali and still charge double. Foil is to protect your forge liner.
Long answer; What ever is appropriate for the foot. Shoes are soft/flexible and have drilled/round nail holes. I most likely used MX 50 or 60. Short answer; Sh!t, I don't know, been 12-15 years since I put any on.