In this first picture, I've stamped some flourishes using the "Perfect Medium" on a photograph. Then, ink over it using a sponge and some distress ink. It seems liked the "Perfect Medium" is working perfectly as resist ink here.
In the second pic above, I've also stamped some flourishes using "Perfect Medium" on a photograph. This time, I've use a sponge and some white pigment ink to lightly dab over the stamped images. The "Perfect Medium" picks up the white pigment ink and shows a subtle effect of the stamped images. I like this effect! Lastly, I've stamped some flourishes using "Perfect Medium" in a pattern paper. Then, I've inked around and all over the stamped images with a sponge and some distress ink. It does not show a very clear "resist" effect therefore, I've used a wet wipe and lghtly wipe the inks on top of the stamped images and it turns to this very cool looking subtle "batik" effect! How awesome is that! I will definitely be using this technique again in my future projects!
After these experiments, my opinions is that, it is preferably to stamp your images on a glossy, semi glossy or matte paper to get an awesome "resist" effect by using "Perfect Medium". If you're using a card stock or a normal paper base to stamp your images, make sure you apply a generous amount of "Perfect Medium" in your process of stamping and work with the inking above it quickly.
Hope this experiments would benefit some of you!