I use a fully enclosed bino harness, the Kuiu one. FHF makes a similar one. My Kuiu one comes with a rain cover too, I'll use that when its down pouring. I also have one of those little soft cloths that are stuffed into a little baggy. I'll use that for when my scope (with the cheapo butler creek covers) or my binos get some drops on them.
This system works for me for the most part. Still seems like in the worst of weather days you can't ever keep up with the drying of water from your optics tho.