You can still load target shells cheaper than the cheap promo shells as well...even with some places selling shot at around $40 a bag...a good 12ga reload - a target shell with 1oz of shot is still around $4.50 a box ...and even the cheap promo shells are up around $6 a box in my area. So you can still save at least $ 1.50 a box over cheap promo loads.
I understand your comments on buffering, layering OO buck into a hull, etc snuffy....but if all you're intersted in is some practice with OO Buck, I still think loading them like any other 1 oz shell is just fine...is it optimum for ballistics, probably not .../ but I'm not suggesting anyone reload "Defense" ammo anyway.
I think if you take the loads I suggest - just using a normal 1 oz recipe ...and drop in OO Buck instead....your tests at 30 Feet or whatever range you want to train at, will be satisfactory, especially for training. But I will admit I haven't tested a lot of OO Buck loads either....