I'm sure you've already checked youtube.... There's quite a few videos on this.
Best bet is to hit up a thrift store (or two) for a cheap toaster oven. Although if the sheet you need is too big, you will probably need some cookie sheets and a full size oven.
Get a good quality oven thermometer so you can keep an eye on the temperature. The smaller the resolution the better. I would check Smart and Final or an on-line bakery supply.
One time here at work, we were trying to anneal some large parts made of Delrin at 400*. The dial was no where near calibrated.... The oven got too hot, the Delrin melted and dripped onto the heater element and started a fire in the oven. No bueno!
I have yet to play with the stuff, but I've got a pack of 8 x 11 black texture here at work....
I just need to come up with a use for it....
Just a thought, but I would consider making a wooden mock up of the pistols if they are valuable. I don't imagine they could be damaged, but you never know.
Good luck and be sure and takes pictures.... Not just the end result, but of the process as well. I'd love to see how this goes for you.