A good video on the whole tintype process is here: http://youtu.be/cXOseY7HxxU
And to start pressing you’ll need a kit like this:
Plus all the associated beakers, funnels etc…
Also check out John Coffer’s website for more general info.
It’s a tricky process at the best of times!
I know a little from building some box/view cameras, but you might have a bit of trouble trying to cover a medium format negative with a lens made for 35mm. You might be able to use it as a macro lens, so you’ll end up with the lens being a reasonable distance from the film plane to get the full coverage of the negative.
An easy way to work out the image circle that the lens creates is to have a dark room with a TV or computer screen on and see how big of an image the lens creates on a nearby wall or flat surface.You’ll see a sharp image with the lens probably 5-10cm from the flat surface. You’ll probably find the circle won’t come close to covering a 6x9 negative unfortunately. I’d suggest nabbing a cheap large format lens of ebay.
Thanks for the kind words, its always nice to get to shot some film on a work trip.