The density fo the substrate you use to put the abrasive on will have an effect on how aggressively the particulate will be.

On a harder surface, the "grit" will sit on top, and be much more aggressive. One a softer surface, the "grit" can sink into the surface, and be therefore less aggressive, and also have some "give" to it when pressure is applied.

That is why I believe the felt is getting such good press lately when coupled with diamond sprays.

I have also experienced good things when using a sheet of paper under my lapping films for the very same reasons. As an example, write ona single sheet of paper, and you can feel every little bump as the pen moves along the desktop. now put a sheet of paper under there, and it feels much smoother, as the paper acts as a shock absorber smoothing out the ride.