I agree on the heat. Get it uncomfortable to handle and wear latex gloves.
I also found that if you pull up on the handle and then lock the bottom lock catch in place you can then move the latch pull-up lever over quite a bit. By off-centering the pull-up lever to the side it's easier to stretch the boot as it has to stretch less.
I also used the half circle end of brake pliers to help get the boot over the lever. Get the lever off-center, lube up the brake handle at the end, stick it into the boot, catch the pull-up lever in the half circle and simply lever the boot over. The roundness of the pliers keeps the boot from being nicked on the inside which is often why the break.