I do not believe it is ever wise to "press" cords from the inside out. And it is is certainly never acceptable to "press" cords on the outside nap. Both processes will result in the flattening or distortion of the "nap lines".
The best way to "press" cords is through a light steaming accompanied by a simultaneous light brushing with a wide horsehair brush, and followed immediately thereafter by the extraction of all the moisture imparted by the steam through the use of a vacuum. This will produce a relatively smooth pair of cords with a light, rolled crease.
Unfortunately, you need a rather specialized European Ironing board with a built in vacuum to accomplish this in the home (they run about $2,000 to $2,500 depending on the brand/model). Alternatively, you could entrust your cords to your local dry cleaner for pressing -- but only if you provide your cleaner with the specific instructions identified above. Don't presume your local cleaner won't put those cords on a press and bring down the head of the press with 80 pounds of pressure, thereby crushing the nap.