Similar to finding locations as a zero-budget filmmaker, props used in your movie are usually borrowed from friends. Because you are borrowing these props, you cannot do anything to modify them. The orange tips on the fake guns must stay on.
Let me see if I can remember some of the props I borrowed. My Dad's friend had an antique looking radio, which he let us use as an "artifact". My friend Alissa's young neighbor had a whole collection of toy guns and swords which he gladly allowed us to use, so long as he could be an actor in the movie. He's probably out of college by now. My friend Mike had some more weapon props for us to use. From my house came shovels and other digging tools. Also, my Mom owned The Golden Dustpan. I don't know why a dustpan needed to be made of shiny brass, but it served its purpose.
Tractors came from my Dad, Mike's Dad, and Alissa's Dad. We filmed the two tractor scenes at least a year apart so the tractor changed in between scenes--from a red and white one to a yellow, black, and green one. Two characters riding on the "same" tractor suddenly becomes totally different. I couldn't make that up. My friend Katie donated a suitcase, since we were at her house for the airport scene anyway.
The reason this post has a suction cup gun at the top is because that is very similar to the model we used. Except that our model was bright orange throughout. There was no way anyone would mistake that item for a gun, but it served its purpose.
So, today's lesson is that any prop you need--even a golden dustpan--ask around and you probably know someone that owns the item that you need.