As Advised Above..A Piece of Glass is Fine..or Marble or Summit..Any Joiners Joint Should be Able to Cut Ya.. Say 22 Cm By 7 or 8 Cm Piece of Heavy Glass..There are 2 Ways..You Can Use One Piece Only as a Base Plate..That Means Using Water Underneath to Suck it Down as it Comes Sticky Back..You Can Remove the Film & Re Use the Same Base Plate for the Full Progression..
The 2nd Way is to Get Multiple Pieces Cut & Just Stick the Film Down Permanently or Until it Needs Renewed..When I was Using Film as a Progression I Used the Former Method..Just Make Sure there are Zero Air Bubbles Underneath..Its Easy Once You Get the Hang of it..
I Hone with the Edge & Heel Slightly Leading for Most of My Strokes..You Can Use Fancy Pig Tail Type Strokes which Involve Both Blade & Spine Leading or Circles..Probably Best to Stick to Edge leading X Strokes Until You Get the Hang of it..You Can Also Use Small Circles Up & Down the Hone on the Lower Grit Hones to Speed things Up..
In Short the Same as Any Hone..Light Pressure is All thats Needed..Dont Go at it Hammer & Tongs..Lapping Film is Quite a Fast Cutter in Capable Hands..
Billy