Are you looking for a guide on how to do it or advice on if it should be attempted?
You might also want to specify the make and model of your phone or the cord you wish to sleeve. Sleeving a cord or wire isn't tough but the tools involved in doing it will take some hefty investment and will require some know how to operate the tools.
To that effect I'd suggest either buying an aftermarket cord and call it a day or talk to those who sleeve them for a living. You could talk to
Ensourced customs.