I also have feet which are blister sensitive, but I'm not overweight.
In principle, everything that 'dampens' your steps, avoids blisters, but cost energy. So it's a tradeoff. This includes for example thick/extra socks, soles.
My experiences with hiking and walking events:
- Not too long, this causes your feet to move inside your shoes back and forward every step, moving your ankles against the back, and your toes against the top.
- Not too short, this causes your toes to touch the front which is an absolutely no-go.
- Not too wide; in the beginning I did hiking events on Meindl's and (at least at that time), I didn't realize they were too wide which causes movement sideways. Not as bad as movement back/forth but still too much after walking 50 kilometers (30 miles) per day.
- Use (soft) soles in your shoes, or even two pairs if you want.
- I like to tie my shoelaces very tight, it prevents blisters since your shoes are fit more around your feet but don't overdo it otherwise your upper feet will hurt from the force.
- You probably want high shoes for stability and prevent injuring your ankles, but high shoes cost energy as you have to lift them up.
- Some people like wearing two socks, one tight, one lose. The benefit is that the tight socks around your feet prevent sliding in the shoe.
- I mostly preferred socks with some padding at the heel and around the bottom part near the toes (so called walking/hiking socks).
- During the walking events where I knew I would get blisters, I taped my ankles, feet and toes in with sport tape. It takes some time to do it good, but it really helps. Of course, every day redo it, otherwise it's not so hygienic.
- Train ... walk a lot, this will make your feet harder or getting used to walking without getting blisters too fast.
- Make sure your feet do not get wet; and if they are, dry them, take some extra pairs of dry socks (when it's sunny, hang the used socks behind your backpack and they will dry, assuming it's sunny).
When it is too late:
- I always opened blisters, sometimes along the trip, sometimes at the end of the day. Learn how to do it good (use a sharp needle, on both sides not in the middle, desinfect afterwards, tape it).
Also you could try walking sticks, the benefits: it takes some load of your feet, so you get less (fast) blisters and it helps your stability too. The heavier the backpack and the more steep the slope, the more walking sticks are efficient.