My son wants to have a weathered/rust look to some of his tractors for a toy show in Feb. The hobby shops were a little overwhelming with their different types of paint that do that. How do you guys do it? Looking for a more affordable way that is 9 year old friendly. (I’m supposed to keep my mitts off of this project) These will be 1/64 size ertl tractors. Thank you!

Pic is a random pic of some MOPARs