I've heard of these techniques as well. Another method, I'm told, is to use steam while stretching. Apparently, all of these take a while, but I have no real experience with any of them. You might ask at a leather store or cleaners.

My impression is that it is important to stretch the material evenly; this is easy for shoes (using a shoe tree), but might be more difficult for pants. Bink's idea of wearing the pants while stretching might help.

Is this userpic of the pants? You look good in them from what I can see.