Tips for shooting in the rain

I have two scenarios that I come across where I might be shooting in the rain. The first is intentional. It's usually something interesting for macro photography, cityscapes, or wildlife. I haven't found a great methodology, so I often elect to avoid shooting which isn't ideal. I have some covers for my camera, but that doesn't always work for shooting at something above me (front of lens exposed to the sky) or for some of my film cameras. If anyone has tips or interesting gear or special tricks, I'm all ears.

The second is the accidental scenario. I occasionally shoot races and because it's a set time and place and I will be there for a few hours, the rain sometimes comes. This happened particularly bad for me when a shot a 10k (Bolder Boulder) and I was caught out in the rain for a few hours. I had a rain jacket and a camera cover but it was still incredibly miserable. I was soaked everywhere, shoes, socks, underwear. Literally one of the worst experiences of my life. Obviously, I would like to avoid that happening ever again, so again hit me with whatever advice you have.