I have oven dried tobacco in the past and it does work, but it is still not as good, in my opinion, as air drying for a couple hours. I have never tried this method of baking the unopened tin that you speak of, but it sounds kind of severe. 190 for several hours I would think would turn your tobacco to dust. Then again, maybe if it is in a sealed tin things would be different. I know that when I oven dry tobacco, i set my oven to 160 for 10 min to allow it to get to temp and then turn it off and bake a few flakes for no more than a couple minutes. Any longer than that and they just get crispy dry and turn to dust when you rub them out. That mistake is how I started making snuff from pipe tobacco he he he. Couldn't see wasting it so I ground it and passed it through a sieve and voila...FVF snuff.