I didn't even see bamaker's question here...
Basically the boil & freeze is pretty simple...
-You need: Boiling water, bowl (somewhat deep/larger bowl to work with is good) of water with tons of ice in it, and you might need a variety of tools like small hobby clamps (ratcheting are good so you can lock them in one "width"), and tools to pick up and move the figures around. Maybe rubber gloves too if you can't stand cold water for long... Oh and figure bases, plain flat ones.
-First you boil up a figure... I use a "hot pot" to boil figures so I'm not basically tethered to the stove while I'm working on stuff. It's a great investment if you plan on customizing, or if you plan on just boil & freezing figures (which is a common need these days since the wide stance is all-too-in with this line right now). If the figure's legs are all you want to freeze (most common need), you can hold him with tongs or whatever so only his legs are getting the boiling if you're concerned.
-Upon removal of your figure from the boiling water, you want to position the figure's limb or part the way you wish it to be "froze", and basically dunk and hold the figure under the freezing water.
-To straighten feet so a figure stands better (I got Commander Cody's feet fairly straight actually, on both the regular and holographic figures), I tend to put the figure on a stand and hold him perfectly "upright" at an "attention" type pose in the water so his legs freeze that way.
-To straighten a wide stance, I like to wrap the figure's hips with the clear "rubber bands" that come with many figures to hold them in packages or hold weapons in place. You could also use the twist-ties in packages as they will be fine in water. I wrap the instrument around the figure at the hip, very tightly. I've also used various clamps to hold the hips in place. This is important, as when you're straightening the legs sometimes the hips stretch and become loose if they're not secure in the sockets.
-I then use the ratcheting clamp to clamp the figure's legs closer together (usually a little more than the position you desire them to be in, as they tend to give a little after they've cooled). I also put the figure on a stand so his feet aren't bowed inward, but instead will lie flat.
-I simply then hold the figure in the ice water till he takes his shape, usually a decent period of time but before my hand falls off from the cold.
You HAVE to do all this relatively quickly though, and like most customizing it takes a certan knack from experience more than something you can perfect right away. Try it on some custom fodder first to see how you do. POTF2 figures were notorious for not standing upright sometimes, so grab a Ceremony Luke and make him stand up like he should, or bend Ponda Baba's arms as straight as you can and see what you wind up with.
Here's a brief list of figures I did recently with the boil & freeze technique, that really are quite difficult to get perfected:
-Clone Commando 7-pack Clones
-Commander Cody & Cody Holograph
-Endor Rebel Commandos '06
Jerjerrod was pretty darn easy actually... The Endor Rebels were difficult because their hips were noticeably loose if I didn't band or brace them prior to freezing, so I had to redo a couple of the troopers for sure.
The Commander Cody figure was damn tricky. Straightening out feet, while also narrowing the width of the leg stance... I got the figure to where I was happy with it, but it's not perfect either. Cody (either version) can now hold a very natural looking "standing" pose, and still has articulation for running or lunging fighting poses. Took some dexterity to get them just right though it seemed.
The Commando Clones were equally difficult. Hasbro's first Clone Commando (Scorch) has 100% different legs than the 3 other CC's in the 7-pack. Scorch stands fairly easily, but my other CC's were very prone to falling over. What I had to do, was freeze the legs (from below the knee more or less) in a more "flat" pose with the toes pointed/twisted more forward for better balance. It took some dexterity again but I managed to get all 3 of the new CC's in the pack to stand quite well, just like their brother Scorch.
Boil & Freeze is something I've done since 1995's figures wouldn't stand... Just knowing the properties of plastic helped me discover that it was possible to make plastic "take shape" to a limited extent, and it's something that's kept me from completely hating some figures over the years. Prime example is MOff Jerjerrod... hasbro really did a crummy job by giving this figure that god awful stance, but once fixed he's a great Imperial that deserves to stand up there with Veers and other neutral stance Officers of their ilk.
I've got Academy Biggs to fix now though I see, lots of Death Star Troopers (I'mg onna be working on those for months I think, haha), Rebel Honor Guard, Snowtroopers, and more. I wish they'd bail on the wide leg pose but Hasbro seems to love it.
So we're stuck.