I suggest using an oven instead of boiling water, unless you feel safer with the water at first. I forget the exact instructions but an oven at like 200, get tongs and hold the piece inside and you can see it become mold-able. I don;t think you need a heat gun. I too suggest trashcan armor, cheap easy and can look really good.
I wonder what style your custom is goin for? If you need help on color, armor style (cause its easy to modify Fetts), gauntlets or weapon choice it helps to know what your mando is used for or look your trying to go for.