Just grab a zip plastic bag and fill it with cold water...Close it...Stick it in the shoe; Put the shoe in the freezer and let sit over the night.
Take out the next morning and your shoe has stretched--Basic Science helps with basic problems.
It works to the degree that you need the shoe expanded at the same rate water expands when it turns to ice - about 9% if my science is still right. And, as any Nor'Eastener or Midwest girl knows, wet/damp+freezing is a sworn enemy of any and all leather.
I'd still recommend a combination of a shoe stretcher and the stretching spray (or a good soaking with some saddle soap combination) to get a perfect fit. And hey, if you don't have a freezer, fill them with oats, or rice - soak the grain and it will expand, that's an old cowboy tricks.