No matter what, you must seal the delay/smoke grain cavity to prevent damaging it. Dog barf in the smoke/delay grain cavity will not do that. Some plugged Loki forward closures (all of mine) have a tiny vent hole to make it easier to insert the smoke grain. The smoke/delay grain is the perfect thing to do that with, but a cast slug of epoxy as mentioned above would work as well.I am going to keep a copy of this reply as proof that not including the ejection charge and using dog barf to fill the delay grain area is a manufacturer-approved modification.
The only place to put dog barf is in the ejection charge well, and honestly it’s not even needed there. A little grease works well there.