I had pretty good luck with the silicon spray on product in the orange can that I bought at the local hardware store for about $8. It worked great on my drift boat covers so I decided to give it a whirl on my uniform this season. I was dry and smiling when most of my peers were soggy and cold. I have used all kinds of spray on and wash in DWR restorer type products from Nikwax and others. The stuff in the orange can is hands down better than any of them.
On a budget, you could do well with used shells and a liberal coating of this product. It will block breathability, but you will stat dry.