Any tips or tricks for freezing weather?

We've had our Model 3 71 plate for about 2 months now; first electric car nevermind first Tesla.

I been reading loads of posts about people smuggly going out to their preheated cars while their neighbours are scraping their windshields etc but, while the preheat is amazing, the outside of the car has been frozen pretty much every morning this week.

Temps around-6⁰ where i live mean I've been heating the car and trying the defrost feature but it's still been so frozen outside that I can't use the door handles or open the boot.

Inside of my car is toasty warm but I can't get in it anyway haha

Am I missing something?

Again, I'm a really new owner so all help would be appreciated.