Schneider Tele-Xenar 180mm f/2.8 Soft filter choice

I have a Rollei 6008 Integral and I want to take some portrait photos with the Schneider Tele-Xenar 180mm f/2.8 lens. Because of the lenses inherent sharpness I want to soften the image using a filter. When looking at a Rollei 6000 lens chart I see the filter size should be 95 x 1. I have two questions. Does the filter screw into the end of the lens? It's hard to tell if there is a thread or not.

I noticed there are several choices of manufacturers (B+W, Schneider, Zeiss) and wanted to know which filter is the best quality for what I am trying to accomplish? I did notice Rollei has the Zeiss Softar 1 and 2 but they are only in the Bay VI size.

Thanks for any help and input,

Michael

Softar 2. Advantage: softness at smaller apertures that diffusers won't have. disadvantage: $$$$. get a softar 2 in a screw mount for your largest and ring down to other glass.