Yeah, the hot water treament works like a charm. I have reshaped countless figures, parts, and accessories this way. It's also useful in loosening up tight joints on figures as well.
I either heat a pot of water to boiling on the stove or, if it's just something small like a weapon or something, heat a measuring cup full of water in the microwave. Dip the part in the water for several seconds, remove, reshape, and allow to cool.
You can accelerate the cooling process by popping the item in the freezer for a couple of seconds.
I've never had any problem using this technique. It doesn't melt anything or ruin paint