A hairdryer to warm and soften the trim as you are fitting it helps. Just take your time and don't rush it.
I've heard that does the trick, but unfortunately I don't have access to a plug socket where I work on the car (shared parking for a block of flats)
with everything going on at the moment though, one thing I do have on my side is plenty of time!
A bucket of hot water and doing it in this sunshine will give you a pretty good shot at it.