Until today, the hardest thing about letterpress printing in my opinion is registration. But fortunately, I came across some advice on Letpress which I found extremely helpful.
When doing multicolor registration, use transparencies. Yes, the same transparencies they use to use back in the day when overhead projectors were in use. I suggest you get the transparencies you can write on because they seem to be the cheapest and work perfectly. I purchased mine at Office Depot for $21 for 100 transparencies. Oh and the best part, they are reusable.
So, how does it work? First you tape your transparency to your tympan and take an impression right on your transparency. Once thats done, you slide your paper underneath the transparency and set your gauge pins accordingly. Once you have finished your run of the first color and ready to do the second color, you tape a new piece of tansparency to the tympan (you can reuse your first transparency by cleaning the ink off with a little press wash). Now take an impression with the second color right on the transparency. Next Slide your paper with the first color already on it underneath the transparency and line up the first color to the second color. Once that is complete, set your gauge pins accordingly. Repeat as necessary. This method should give you almost precise if not exact, registration.
Please leave a comment if you would like me to explain further. Pictures will be added later.