If location of weapon is not reasonably known, will an EISS still be conducted?
No, however BT should take measures to ensure their saftey.
When a weapon is found, what steps should be taken to secure it?
Engage the safety, remove ammunition, use the push/pull method to ensure there are no rounds in the chamber.
What should you do if you do not know how to unload a found weapon?
Ask if anyone on your team knows, and if not, hide the weapon and post a guard to secure it’s location.