Many apps have an auto-reload feature. As soon as you save your PSD, the 3d app sees the datetime change, and so it reloads it. Dual monitor setup helps a lot with this... Photoshop on one side, 3ds Max or Maya on the other.
It may sound stupid but how people see changes they make in Photoshop on their 3d models immediately? Do they use 3d mode in PS? All tutorials on texturing I saw were in Substanse Designer/Painter, Modo, 3d Coat etc. Now I've decided to learn an old-school way to do things and the only way to see changes on the model I've…