For 5X7's I peel up the ruler and put it at the 5" mark and cut a 9 1/2" X 5" piece. Then I click with my fingernail to set the 7" end where it needs to be for the final cut. 4X5 I wouldn't bother with. Too fussy. But I do 6.5X8.5 all the time. The least waste film of all. Roll out and cut your 6.5 length and then trim an inch off for the 8.5. Really slick! 5X8 would be very easy also. 7X11 is easy but wasteful. You have to cut at the 11 then trim your 9.5 down to the 7, so 2.5X11 waste on those. Still, I do it all the time.
Oh, I do everything emulsion side down. Clean clean clean. I don't use white gloves, the tactility is too necessary. Cut film after you wash the dishes and your hands are clean and soft.