When I first started using Maco IR film I didn’t get consistant results until I shot off a test roll. I simply set the camera up on a tripod and fired off a roll of 120 having taken a light reading at 100 ISO which suggested 1/30 at f22. This equalled the sunny 16 rule. That was my first exposure, and I worked through the roll, doubling the speed for each frame, but keeping the same aperture. The last exposure was around 1 minute. I developed the roll in Prescysol EF and then selected the best frame. This turned out to be the one taken at 2 seconds, which by my calculation rate this combination at ISO 0.75 from that I can happily calculate exposures for other lighting conditions. All this was using the opaque infrared filter, the number of which I can never remember, but I think it’s 780.
I think the film that Rollei are marketing is a faster version of the stock that I have, so my figures may not apply, although the test method will.