Breaking in new cowboy boots

I lost my cowboyboots of like 10 years durring a move. Wearing them was like I was weightless, and im on the husky side. Just broken into perfection. I could be on my feet for 12+hours with them.

I got a new pair recently, but this time got a fully leather sole instead of rubber. But my feet have been killing me. Does anyone have any experience on how to expedite this? I've heard of using conditioner or wearing them while they are wet but cant find any real testimonials on a good approach