I use a standard house iron. NO STEAM. cotton setting. once up to heat, it melts the foam, and eases the paper glue (I think) which when cooled, becomes stiff. a metal rulers speeds the cooling, reduces the wrinkling that happens around curves and straightens a gentle buckle that sometimes happens. It is as fast as 45° cutting and faster than sanding or cutting a thin wedge. It also make peeling the paper off easy while hot. and harder when cooled.
On the beveled fold-over edge I usually remove paper on one side to allow for crushing, but the other hardened edge helps with stiffness.