I walk around in mine the first day then just ride
I just got a new pair and I've been wearing them around the house just walking normally and just after a day they already felt normal and I put band-aids on the back of my heels so they won't blister and so far I haven't felt any pain!
I would wear them around all the time. Another stretch to do with them on is step up on a stair, put the ball of your foot on the stair and stretch your heel down. That helps simulate the feeling of a stirrup and could possibly help break them in.
That's what I would do, hoped it helped!
Pick a hot day, stand in a water bucket until your toes are soaked, then ride in them until they're dry. Fastest and easiest way of breaking in boots I've found so far! It sounds terrifying but I've broken in some very expensive boots this way and never had a problem. Only thing is you have to keep them on until they're dry :)