Make shift oven...
Grab a medium or large box from Lowe’s (whichever one has the blue outline), a piece of pvc (6” long or so )pipe that large enough for the tip of a heat gun to go into. Some hvac aluminum tape. Cut a hole around the bottom side of the box for the pvc to go into snug.. then use the hvac tape to tape and seal the box. I then use a cheapo meat thermometer stuck into the top and monitor temps that way.. sometime you gotta pull the heat gun out some of temp get to high etc.
I work on the road most of the year and only go back home every month or two for a week at a time so this is how I’ve managed to do it in a hotel room without spending a fortune.
Using just a heat gun you’ll screw those housings up.. permaseal needs constant and several heat cycle most times to break it lose its to easy to heat and melt the plastic up.