the raised dots are from debris either on or more likely under the film. It is toast. Gotta keep everything very very clean.
I took an old 4" wide putty knife from the basement and polished it on the wire wheel and then honed it to lay very flat on my granite lapping stone. Before positioning my lapping film, I will spray on clear water and squeegee it off with the putty knife. No dust dirt or debris left behind and no more ruined film after a couple of strokes. You could use any thin flat tool. I bet one of those hard plastic "Bondo" spreaders from the auto parts store would work well.