First of all razors that come from shops are usually honed at the factory. Generally, not always, shave ready. You may want to have it honed or strop the heck out of it.

Second, your strop sounds like a loom strop or some kind of paddle, pics help. It also sounds like the light part is untanned hide and the red is some kind of Latigoed hide. Generally you would apply strop dressing, or other abrasive to the untanned side and the tanned side becomes the stop. Or you could go the other way. The tanned side will probably have more draw than the raw side.

As far as painful, watch your prep, your angle, your pressure and your edge.