In reply to Turdus torquatus:
I am about to demonstrate that a picture is worth a load of my waffle.
Bar is pocking inside boot with a padded end pressing against the bit that needs stretching. The rest of the bar, the bar is about 40cm long in total, is outside of the boot, where your ankle would be, but has a great big block of wood fixed to it. Turn it upside down so wood block on floor, bar pointing vaguely upwards, boot upside down speared on the bar.
Two long cable ties, they are about 1m long but nearer the 0.4 length of bar when done up, looped around either end of wood block and either end of boot (toe and heel). As you tighten the cable ties it pulls the boot against the bar.
You can get a lot of pressure with cable ties, in fact too much so have to be careful. These are releaseable one o after 10 minutes you can unclip the release and un thread them and then take the boot off the bar.
You should be able to achieve the same by just threading the boot onto the bottom leg of a bar stool and pulling against it or turning upside down and pushing. Its just I made up a Heath Robinson version because I have to do it every time.
If there is not a plastic toe cap then most likely may not need to heat the boot, just stretch it.
Years ago I worked this out when every time I took the boots to be stretched at a cobblers they were OK but then within an hour or so went back to how they were. I rang Scarpa who suggested the pan of boiled water and plastic bag.