Field Jacket Liner How To Waterproof A Jacket?

How to waterproof a jacket? - field jacket liner

I have an old military field jacket is the outer layer 50% nylon and 50% cotton Lining: 100% cotton. This is an incredible jacket is warm enough to use the bulk of the winter with a removable liner, but light enough to wear in spring and autumn, but not too hot. The only problem is that poetry is that there is a kind of thick so it takes some time to remove water, where it bothers me is. Does anybody know some good products for the sealing of this matter?