I regularly achieve HFOs by actively clenching my pc muscles. I start clenching at the last part of the file, when she starts describing the blowjob or intercourse. Preferably she mentions triggers such as clench or snaps her fingers, which I can clench to, if not I just clench at every moan or suck she makes and try visualize her wet cunt or mouth. In the end I accelerate the clenching and buck my hips a little (but not as much as my cock starts slapping around) and wait for her to say something particularly dirty, that turns me on (e.g. she tasting her anal creampie or cum drooling all over her slutty face ruining her makeup) and then I orgasm.
my favourite files are
daisyroseviolet - pleasure room
alwaysslightysleepy - phantasorgasmigoria 1 and 2
belle in the woods - teasing you to a hands free orgasm
misscherrykai - one little word
orgasmic giggles - your beatiful cock
orgasmic giggles - end of your world
eves garden - no joi for you 3
for me good dirty talk trumps a perfect induction by far and I always look for performers in my age range, I cannot stand these +40 yo smoker voices.