A ferrotype tin is a sheet of flexible steel, highly polished and chrome plated on one side. They must be kept immaculately clean and be completely free of surface defects. The emulsion side of the paper is pressed into close contact with the polished side of the plate. Any air bubble or bit of dirt will ruin the ferrotyping job. This is not an easy thing to do. I've had better luck using a sheet of plate glass. It's easier to clean, and not as easy to scratch. The downside is that you cannot put the glass in a print dryer, so you'll need to be patient. When dry, the print will have popped off the glass or plate. If it doesn't, then something is wrong.
A well executed, ferrotyped print will have a finish more glossy than the slickest of glossy resin coated papers and is, to my eye at least, beautiful. They look best as small to medium sized prints, no larger than 8x10. The best paper for the job is single weight fiber which is very rare today. Perhaps the technique can be used with double weight papers as well. Freestyle is selling single weight, glossy, fiber based papers from Slavich. All are graded, not variable contrast papers.
Thanks for the info.