Most blisters from new shoes occur from stiff material digging or rubbing your skin. To help break in shoes without sacrificing your feet, a trick I learned in high school selling shoes was to first break down the stiffness in the back of the heel by ‘folding over’ the material. Push the back of the heel down into the shoe and ‘roll’ along the seam to break down and soften both the back seam and along the top edge. Soften the ball area of the shoe as well by bending the shoe repeatedly where the ball of your foot bends. Once you get blisters, the only thing you can do is cover them. The sooner you cover them, the better, and if you don't have access to bandages, use whatever you can to pad the rubbing area. If I'm hiking and getting a blister with no bandages, I'll pick some large, soft leaves from a plant and pad the area. For shoes that have a rough spot that irritates, try using a soft piece of cloth cut to shape. Apply rubber cement generously to the rough spot on the shoe and one side of the cloth, let both dry then press cloth firmly to shoe (this is called dry mounting). The rubber cement stays flexible.
Stretching Too Tight Shoes
You don't need to buy the expensive liquid from your shoe repair store that stretches out tight shoes. What it contains is almost exactly like rubbing alcohol but they put a huge price tag on it with a fancy label. Simply pour some rubbing alcohol into your shoe to saturate the inside, put the shoes on while wet and wear until well dried. To stretch a little more, repeat the process. Before doing this, you may want to do a patch test on a hidden area of the shoe to make sure alcohol does not damage a fabric color or material.