Hi,

I recently started playing again after a long break from guitar and I was unable to play for more than 20 minutes without finger pain. I was also unable to bend the strings more than a half step. However, I found the quickest way for me to "callus up" was to play through the pain for a good 30 minutes to an hour, forcing myself to bend with the goal of a full step.

If I remember correctly, it took less than a week with one day of rest in the middle, so around 4-5 hours of torture. It helped that I had some experience and could pick a couple of songs to play repetitively to kind of take my mind off the pain rather than just bending for half an hour.