After installing the deck railing and staining the deck, I'd spent the evening watching reruns of BBQ pitwars. Everyone injected pork but it appeared that these fluids were either room temp or chilled, transparent and I would think, at a point, the bacon fat would try to solidify and not mix as well as these looked. But I would think it would add some really nice taste
Make no mistake, there ain't no powder in this Puff ! And... I'm not really a crazy person but I play one in real life
you could inject it hot immediately before putting on to smoke. The injection will set quickly with the cool interior of the shoulder meat so you wont need to worry much about marinade running everywhere. I would try 3 parts bacon fat to 1 part cider vinegar with your seasonings added in (add some brown sugar to the mix) Dang, that is painting a pretty picture flavor wise.
Nothing to base this on, just sounds good enough to try
If it can't be smoked .... try frying it. It that don't work, it's probably best just left alone