Here are some other weathering tips that didn't quite fit in any of the other sections...
If you’re going to weather a kit with decals it’s important to weather those decals as well. A scratch or faded decal can add a lot of depth to the look of a kit. For the most part, weathering and stickers don’t work well together as weathering tends to accentuate the sticker’s border.
The simplest method to distress a decal is to scrape at it with pointy end of a toothpick or similar tool. It’s important to make sure that they’re fully dry and set with decal set solution before doing so. Don’t scrape too hard, you don’t want to mess up the paint. Note that your surface is heavily chipped, the decals should not cover the chipped area, as the paint would normally have worn off there as well.