Masimix,
attached a scan of a somewhat dog-eared print from a Sabattier-ised negative (or solarised - take your pick). 120 format film, shot in dark on flash. About half way through development I switched off the darkroom lights and removed film from tank and took it off the reel. When holding it horizontally in from of me, I got my wife to switch on a shaded table lamp and off again after counting to two seconds.

I then re-loaded the film to the reel, replaced in tank, switched on darkroom lights and finished the development. This prints as normal negative.

It's actually pretty easy, but I'd say that I was probably lucky in not over-exposing with the flash.

I've tried a few times to create sabattier effect by flashing prints when in developer, but with varied success.

I attach an example print (erroneously entitled blue solarisation) which was done using toners and not through exposure to light.

Hope all this helps,
Niall