I have a Finney pinhole body cap from Calumet that I can use on my Canon FD cameras (or any other cameras with a little gaffer's tape). It's of known size, so that's handy.

My usual setup is to use it with an old shoe-mount Voigtlander Kontur finder for framing and 1600 speed film of some flavor. That usually gives me around 1/30 sec. in bright daylight.

I try to shoot pinhole in hard light to get that pinhole glow off bright objects.