Well, don't use pliers with those. Just rub them flat on the sheet. If you don't press very hard, just a sweaty or licked finger on the reverse should be sufficient to move your disks forward and back. If not, a cone of BluTack will do it.

I also think your choice of grits too fine(see my suggestions above) The 3600 will already give a near mirror finish and the 12000 might be too fine to have any effect at all.

They gradually become smoother with use too and move up a grade, so all you have to replenish with time is the lowest one. Dennis.