Murry,(posted 8275 days ago)The platinum process used most often actually contains palladium, or a mix of platinum and palladium. Either way, the paper is coated using a brush or coating rod.
The negatives used for this process can be in camera negs or enlarged negs. The main problem with using negs developed to print on silver paper is that the pt/pl process needs much more dense negatives to take full advantage of the extended tonal range of the process.
I make enlarged negatives from 6x7 negs by making a 4x5 positive on ortho film and then make the final contact neg using lith film developed in PMK Pyro. All this sounds complicated, but it really isn't that hard if you want to do some research.
If you want to get into this process, go to Bostich & Sullivan on the web. They offer kits to get you started. They have a Ziatype kit, which is a Print out Process using platinum or palladium. They also have the book, The New Platinum Print which is an excellent guide to making your first neg and print. I also recommend you order step wedges from them so you can fine tune your begs without the hassel and cost of always printing them to see the result. The people at B & S are a wealth of information on all sorts of alternative or historical processes and they have the chemicals you need.