Create the look of heavy wear by using abrasives, heat and chemicals
Use sandpaper to rough up the garment, especially in areas that would see the most friction and wear. Keep the fabric taut and steady to get the most out of sanding. Place shapes under the fabric to mimic wear patterns. For instance, place a tennis ball under the fabric to mimic elbow or knee wear. Place a thick wallet or chewing tobacco container in the back pockets of jeans before sanding. Foam sanding pads can be easier to hold and can help put more friction on prominent areas of the garment that would see the most wear.
Use a rotary tool with a wire wheel or a sanding tip to create heavily worn out areas in hems and seams. A sanding tip works best on the edges of baseball cap brims. Thin fabrics or loosely-anchored fabrics might get caught and twisted in the rotating bit.
Brushing pulls some of the threads out of the weave of the fabric and can help achieve a pilled look from years of friction.
A serrated pocket knife, flooring knife, or kitchen knife helps create random tears and wear.
A curry comb is a horse grooming tool that resembles a handle with concentric circles of saw bands attached to it. This tool could be a great off-the-shelf tool for doing heavy distressing of heavier fabrics.
Developed by German post-apocalyptic costume designer Dmitri Zaitsev, the zerfetzter – German for “shredder” – is made using a hole saw drill set. Some users may prefer leaving the makeshift handle off and just grasping the outsides with their hands like a scrub brush.
Steel Sanding/Rasping Tools
For heavy friction, use a steel sanding sheet like Dragon Skin, a multi-rasp shaver, or even a cheese grater.
Sometimes the least artificial methods work the best. I’ve seen some great moth-eaten patterns created with the spray of a shotgun round.
The flame from a gas torch can singe edges, oxidize metal hardware, burn or melt holes, turn fabric crispy, and even lighten the color of the garment.
Sodium Bisulfate is a chemical used in a method called burnout, or devore, in which patterns are created in fabric by chemically disintegrating cellulose-based threads. One popular brand of sodium bisulfate burnout liquid is Fiber Etch, but you can make your own at home by purchasing the powder form and mixing it with glycerin.
You can create a moth-eaten pattern by spattering the sodium bisulfate on a cellulose-based garment, or create a pattern of sheer areas on a garment made of a cellulose-synthetic blend, such as polyester-cotton. The chemical requires a heat source (hot iron, heat gun or hot dryer) to activate. Washing removes the weakened fibers.
Hydrochloric and sulfuric acids burn holes in garments, but they are very corrosive and therefore dangerous.
Bearings and salt water
One tip I have yet to try is to soak steel bearings (like BBs from an air gun) in saltwater, and then leaving them on a garment for a few days. Apparently the salt reacts with the steel to create a corrosive effect. It would probably also leave some rust stains.
Washing & Drying
Always put your garment through a wash and dry cycle to get the most fraying out of your cuts and damage.