I have great luck using Kroil as a penetration oil.
If the gun works fine, shoot it.
If the nipples are seized, be prepared to possibly ruin them getting them off, have spares on hand unless you don't mind waiting to replace them.
I have destroyed two dedicated nipple wrenches in the past, I'd like to see your home made wrench if possible.
I think I may end up trying the acetone/tranny fluid mix.
Here is a pic of my homemade nipple wrench. A dremel to 3/16" socket. Been using this or one like it for years. Much stronger than the store bought ones.