Well, since there are not grunge colors in the line you’d have to mix them.

For the most part you’ll add brown, black, or grey to something that’s close to what you want. You’ll have to experiment and keep notes so you can reink the pad once it needs more juice.

It might be best to experiment on a NonStick Craft sheet with tiny amounts of color from the reinker to see what the proportions of each color need to be.

The other option would be to text mix with the colors from the paint line, which will get you close. None are really an exact match from one line to the next, but it’s a jumping off point.

For rust I would try Fired Brick with one of the browns, probably Ground Espresso. Add tiny amounts of brown at a time till you get what you like.

For barbed wire, (assuming we’re thinking of the same color), take your rust color and add some black. Tiny amounts.

Dark brooding storm clouds… Weathered Wood deepened with a touch of Chipped Sapphire, then add Hickory Smoke.

Or, you could ink the pad with shapes of color as you suggested with the dots, squiggles, etc. No idea how that will work, so it will be a real experiment!

I don’t know what the recommended use time is on the Ranger products, I’m sorry.

Ranger’s CS folks should be able to help with that information.

Having said that, I have most of my original jars of Dylusions Paint and have not seen color degradation or significant changes. Same with some of the colors of Distress Paint that I don’t use all that often. I’m careful to keep an eye that they don’t get dry and I keep all of my supplies out of the sun as a preventative measure.