Sanding only works on clothing that has a lighter color woven into it, like denim or in the case of leather, where the top is darker than the base. Dry-brushing is the paint equivalent to sanding. You are taking a lighter color and applying it just on the high points. This mimics the look of the material being worn without actually wearing down the surface. It also creates contrast which highlights the raised surfaces. We use this in theatrical painting to bring out the details of an object all the time. I call it "theatrisizing". A wash is usually darker than the base color and is heavily diluted. When applied, it goes into the low points. This creates a deeper look to the details. Now both of those examples are for hard surfaces and basically just bump the contrast of an object. Soft surfaces act differently. Try brushing is about the same but washes on fabric become more like dye becuase the material absorbs the color. And no, there is no erasing of washes on fabric. Unless you wash the garment before it dries which is not a good idea sometimes. Dirtying clothing is almost the opposite of what I just listed above. Things like dust and dirt often aren't totally on the surface but actually in the reassess. That's where an airbrush can be of benefit.
I am by no means an expert on this. There are tons of customizers here that are better than me. I just apply what I know from my other profession.
With all techniques, practice is the most important thing to do. Especially when working on one of a kind items. Also reference material is can be a great benefit especially when starting out. Instead of "creating" the effect, with research you are more or less replicating it which can be a lot easier. Definitely more accurate. Google images of the real thing and have them in front of you while you work.
Good luck.
