I use a R72 filter, This has a 4 stop filter factor.
This means to me rate at ASA 200, meter at that, then open up 4 stops (Effective speed 12.5) before plopping the filter on
I find on a sunny day that handheld is fine.
Easiest way of shooting SFX is using a non SLR camera.
The old style 35mm with separate viewfinder is easy, a Twin lens reflex for 120 is even easier if you like shooting MF.
Shooting with a SLR is possible. I've even done action shots of birds of prey like this on an old Praktica. I just sighted over the top of the camera.
Without a filter, on an overcast day the film will look like normal B&W. On a really hot day, it can give some slightly odd effects. I've shot pictures of a castle where the railings were painted black, and therefore got quite warm. Even without the filter they printed out like neon strip lights.
Also portrait shots can look a little washed out, as it gives surprisingly ghostly white effects on caucasian skin without a filter.
One shot of my daughter for instance caused much consternation...
"Daaaad you made me look like a *Ahem* Goth" Charming child! I blame the parents
For portraits of afro-caribbean skin the results can start to edge towards an albino effect (Especially with the filter)