Custom orthotics every single day from the moment my feet exited the duvet. Foam rollering calves. Ice packs and a lacrosse ball under the feet, along with lots of non weight-bearing upper foot and toe stretches.
New footwear - running shoes a size larger to allow for the orthotics - Clarks (not heeled, flat with a separate half inch thick rather than thin sole) tend to be large enough to be able to lace up in terms of formal shoes, as the uneven wear pattern on older shoes increases instability. They also need to be lace ups so you aren't having to grip with your toes to hold them on or have your foot sliding around in them. Walking boots/shoes are also very good in terms of support.
The previous time I had it, I needed to wear a cast to stop my ankle moving around too much, as the constant wobble and overstretching of overpronation was what made it so bad. Being able to sort it by chucking everything but the kitchen sink at the problem as soon as the twinges came was a whole load better than that - and steroid injections had been useless (ridiculously painful, too), so I wasn't about to repeat that mistake.
I also made a conscious effort to adopt more of a mid-forefoot strike rather than landing on my heels and all impact related exercise was off the menu until I wasn't feeling any pain - so swimming, rowing and weights were my exercises of choice. And if I would normally stand up for something, I'd sit down instead rather than risk further unnecessary damage.
The memory foam shoes feel nice initially, but they make your foot even more unstable, rather than supporting it in the position it needs to heal, so they make it even worse.
You can't assume it'll just go away, as if you still wear unsupportive shoes, every time you put your foot on the floor you tear some more until you actually feel your entire arch dropping to the floor as it's torn through. The people who have it disappear without consciously doing anything are those who have been very lucky.