McCormick - Deering Model MF grin drill

I'm thinking about interseeding the pasture later this fall or early next spring with some more grasses and legumes to help thicken the stand and increase the diversity of what's there. Ground is really, really light and dries out fast. In the manual for the drill, it mentions increasing the pressure on the ground openers for using it when "stubbling in" in untilled ground. This sounds to me as though I could use this drill to do my interseeding, which would be much cheaper and simpler than renting/buying/hiring a real interseeder, and more efficient than just broadcasting. What do you folks think?

Second question. Anyone know where I could get some replacement seed tubes? I have a couple on the main seeder that just hang up everytime I raise/lower the unit, and all of the hay seeder tubes are missing. I pulled a spike tooth drag behind on tilled ground when planting the hay to give some coverage to the hayseed that I just allowed to fall out the bottom of the hay seeder bin when I planted - worked OK, but I would like to be able to direct the hay seed into the shoe so it goes into the slit made by the opener in the future.