I'm wrapping in my garage and winter temperatures are between 50 and 65 degrees.
I can heat the flex coat prior to mixing, but the area I apply it is cooler.
Can I thin it, and will this help?

Do I need to heat the garage for it to cure overnight?

Any tricks that will be helpful?

It really won't do you much good to warm the finish only to then try to use it in an area that cool. And thicker finish is a bit hard to apply. It will also take a long time to cure at such low temps.

Yes you could possibly thin it a bit with a few drops of acetone. Generally, epoxy manufacturers (actual manufacturers, not sellers) do not recemmend adding solvent to epoxy. However, because it will take such a long time to set, most of the acetone should be out of the mix before things set.

Still, your very best bet is to store your epoxy and do your finishing in an area where temperature is 65+.

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I had this problem, and solved it with an old unused electric heater. I keep it on when I am working in my basement. I can keep the temp above 65 except on the coldest days. Then, I break out the kerosene heater. Haven't had to do that this year so far, the electric one does a great job. I turn it on about an hour before I do anything involving any type of epoxy, either adhesive or finish.

You could also run into a hazing problem (micro air bubbles being trapped in the finish) Many years’ back I was doing my finish by a window the temperature in the room was anout70%. T next thing I knew, the finishes started hazing. To me there was know reason for this to happen until I realized the temperature by the window was 60% do to a draft. I had creaked the window.
Good Wraps Bob