Before you do anything, read the paper patching book by Randolph Wright (don't remember the title exactly) and The Paper Jacket by Paul Matthews. This will get you started on the path. Past that, you need to realize that most paper patch bullets are and have been fired from black powder rifles. The techniques of using black powder and using smokeless powder are quite different, the bullets are completely different, and nothing much except the basic concept is the same. Do not get the two confused, or it won't work.
As for onionskin, that is the thin cotton paper that secretaries used to put between layers of carbon paper when they needed to make multiple copies of something on a typewriter. It is seldom used any more, for obvious reasons. The source of it in the US is The Paper Mill, and they sell a 9# ream of it for about $25 over the internet. I have never seen it available locally. It will add .006" to the diameter of your bullet when wrapped properly.
So, see if you can find those two books, study them well, and see what questions you have from there. Enjoy yourself, paper patching is a long road with a big learning curve. Most every tool you use will be custom made for your particular gun, and almost nothing you use will be available off the shelf. Most first time efforts produce terrible results. (My own experience mirrors this - my first tries couldn't even keep bullets on the range, let alone on the berm.) But if you keep at it, you will eventually get good results and find you have no need for jacketed bullets any more and be able to astound your friends at what you can do with simple soft lead cast bullets.
