1. Shoe lace (Braided) (2 nos)
2. Cellophane tape
3. Super (Cyanoacrylate) glue
5. Love for your mac and Some extra patience!
Cut a small piece of paper and wrap it around the power connector and the wire clip of your power adapter. Apply cellophane tape around it and make sure that the taping is smooth and easy to slide through the lace (no sharp edges and protrusions).
Take the braided Shoe Lace and squeeze it gently near the end so that the braids expand and the hollow space is formed inside the braids.
Now slightly open up the expanded braids with a pencil tip and insert the Cellophane taped end of the adapter. Once it enters into the hollow tube of the lace, gain more patience and slowly squeeze and push the lace up the wire till it reaches the end of the lace. Now, take the next lace and repeat step 2 and 3, till the Laces cover up the whole length of the wire till the white box of the adapter.
There will be some extra shoe lace hanging. You can push in the whole lace or cut it and finish it neatly with some tape and super glue.
Cutting the braided shoe lace may become a messy issue, if you are not careful. The best way is to apply a little super glue for about 10mm length on the lace and then cut it once it is dried up. REMEMBER: IT IS BETTER TO MEASURE THE REQUIRED LENGTH OF THE LACE AND CUT LIKE MENTIONED ABOVE, BEFORE INSERTING THE LACE INTO THE WIRE. or, you have to be very careful when you are applying the glue onto the lace inserted over the wire. Otherwise, the lace will stick strongly to the wire and it may damage the wire.
You can try other glues, tapes or knots to finish the end neatly.
Voila! now your adapter wire is dirt resistant!
PS: If you want to guard the box part of your adapter, you can take an nice colored ankle sock and use it to dirt scratch guard your mac's power adapter.