hey leo ,
i've used both a heat gun and a hair straightener . i think , based on my personal experience , that a flat iron works better . haven't done it in a while , but i seem to recall i used it on high setting . pretty sure you can google it to be sure of the setting . i think something from this site comes up if i remember correctly . i just kinda do 2 "sides" and check visually every few seconds .
good luck ,it's not a mistake if you can fix it !
thanks , jim
Listen to the river sing sweet songs to rock my soul ...