I have had luck w/Birkenstocks and my PF......wear them almost 24/7 in warm weather and inside during colder months (and New Balance sneakers for outside). My PF is basically gone (or at least under control). I also ice my arches/heels every night after a long day of walking (like at WDW!) and have never had issues w/my PF flaring up on a trip <<knock on wood here....lol>>
Good luck and best wishes w/your PF!