From lots of experimentation and experience, I would say the Sapphire effect is actually rather poor at this. It creates an obvious “film effect”‘, which might set off alarm bells with the network. I would avoid using their deinterlacing filter or their Film Motion Controls. The grain, gamma and exposure controls in Sapphire’s Fim look however are very good, but you need to dial them down a lot from the default settings to be convincing.
I have used the method Bouke suggested…apply a Time Warp effect, leave the speed at 100 percent, then set it to Fluid Motion, Interlace in, Progressive out. The result is usually very convincing. Render is very very slow, though.
You should also render it before doing any color correction or applying any other filters. If you cannot afford the colossal render time, or are getting strange artifacts (fluid motion sometimes does that depending on the footage) you might try Interpolated field instead of Fluid Motion. It renders much faster, but the quality is not as high…but may be acceptable depending on the footage.