Guys i need some experts help here. 1. Two nuts on each of my front doors hinges have started to show some rust in them. I want to prevent further damage. What can be done? 2. I don't have mud flaps in my vehicle hence i could able to see some black dots (I guess these are thar sediments) on the bottom of both front doors as well as the bottom of rear bumper. Btw i am currently using the Jopasu car cleaning solution (Pink color) for washing my car. I am able to remove some black dots with lot of effort but still the left overs are visible. Is there any solution to remove these substances?