Shaping my Boba Fett back armor

Hiyo!
I'm looking for easier ways to shape my backplate for my ROTJ Boba Fett armor. I'm using 3mm ABS plastic, and my last backplate's shoulder parts were heated up over the burner on my oven, that I fit onto my back, leaned against the wall then pressed onto my shoulders. It was far from the best and real uncomfortable. I'm hoping there's an easier way, cause my next step is to make a plaster mold of my back/shoulders and use that as my template. Thanks! I've loved this site for years for my previous Fett costumes (I've done flimsy placemat and sheetmetal armor but this time I want it to last).
Tks

Buy a heat gun, like you find in the paint section of the hardware store. It is easy to spot heat and control how much heat you use. By far the best way I have found to heat and mold sintra.

Thanks. I'll give the heat gun a try... sounds way easier than what I've been doing.